Torque Converter Clutch Circuit Stuck

What Does It Mean?

Modern vehicles equipped with automatic transmissions/transaxles use a torque converter between the engine and transmission to increase engine torque and drive the rear wheels.

The engine and transmission are actually connected by a fluid coupling mechanism inside the torque converter, which multiplies torque until speeds equalize and create a “stall speed” where the difference between actual engine speed and transmission input speed is about 90% efficient. The Torque Converter Clutch (TCC) solenoids controlled by the Powertrain Control Module/Engine Control Module (PCM/ECM) or Transmission Control Module (TCM) direct hydraulic fluid and engage the torque converter clutch to create a solid coupling and increase efficiency.

The Transmission Control Module detected a malfunction in the circuit that operates the torque converter clutch solenoid.

Note: This code is similar to codes P0740, P0741, P0743, P0744, P2769 and P2770.

There may be other diagnostic trouble codes associated with the Transmission Control Module that are only accessible using an advanced scan tool. If additional transmission-related DTCs appear in addition to P0742, an electrical failure is likely.

Symptoms

Symptoms of a P0742 trouble code may include:

Malfunction Indicator Light (MIL) is illuminated (also called check engine light)
If the torque converter clutch is actually locked, the engine may stall at idle. This is a common problem for some GM vehicle models, when driving at highway speed, then the engine stops, with the torque converter clutch locked. Usually, the engine restarts and resumes normal operation.

Potential Causes

Causes

of this DTC may include:

    Wiring harness to the transmission, damaged, pinched, or shorted to power
    Torque Converter Clutch (TCC) solenoid failure
    Transmission Control Module (TCM)

Diagnostic Steps

for P0742

Test the control circuit wiring between the TCM and the wiring harness connector in the transmission case using the DVOM set to the volts scale – it may be necessary to remove the pin from each side of the harness connector to isolate it from the harness while it is still plugged into the TCM and transmission case. With the positive lead at each end of the wiring and the negative lead to a known good ground, check for battery voltage with the key on/engine off. If voltage is present, suspect a short to power and determine the source of the short in the wiring harness.

The DVOM should be set to an ohms scale with the positive and negative leads on the TCC power and control circuit pins. The resistance should meet manufacturer specifications; if it is very low, it may be necessary to remove the transmission oil pan to inspect or replace the solenoid inside the transmission.

Transmission Control Module (TCM) – Since the torque converter clutch is only engaged under certain driving conditions, it will be necessary to monitor the TCM with an advanced scan tool to determine if the TCM is commanding the TCC solenoid and what the actual feedback reading is to the TCM. The TCC solenoid is normally controlled by a duty cycle to achieve a more comfortable torque converter lockup engagement.

To test if the TCM is actually sending the signal, a graphing multimeter set to duty cycle or a digital storage oscilloscope will also be needed. The positive lead is probed into the wiring harness plugged into the TCM and the negative lead to a known good ground. The duty cycle should match what is commanded by the TCM in the advanced scan tool reading. If the cycle remains at 0% or 100% depending on the circuit used, recheck the connections and if all wiring/solenoid is OK, the TCM may be faulty.

P0743 Torque Converter Clutch (TCC) Solenoid Valve Electrical

What Does It Mean?

This diagnostic trouble code is defined when the engine management computer (ECM), also known as the powertrain control module (PCM) and also referred to as the engine control module (ECM), detects a failure in the electrical circuit of the torque converter clutch (TCC) solenoid, which is located inside the transmission.

An automatic transmission is not 100% efficient because it is a hydraulic coupling that connects the engine to the rest of the internal transmission components. The torque converter transfers power using hydraulic force and is internal to the transmission assembly. This power transfer results in excessive heat. The lock-up torque converter was designed to make the transmission more efficient at highway speeds and to control heat. The torque converter clutch is what locks the converter. Heat kills transmissions. This is why you hear that stop-and-go traffic is hard on an automatic transmission.

The torque converter clutch does not lock at these low speeds, so heat is generated. This clutch is controlled by an electrical solenoid. The torque converter clutch is locked, changing the hydraulic coupling into a mechanical coupling. This solenoid uses power and ground sent through a coil of wire that creates a magnetic field to pull or push a central metal rod. When the solenoid is energized or de-energized, it directs the flow of fluid through the transmission valve body.

Symptoms

Symptoms of a DTC P0743 may include:

    Malfunction indicator lamp illumination (check engine light or service engine soon)
    Stalling when coming to a stop after cruising speeds
    Shudder upon takeoff
    Shudder when stopping

Causes

Potential causes may include:

    Low or dirty transmission fluid
    Wiring/circuit issue shorted to power or ground
    Faulty torque converter clutch (TCC) solenoid
    Failure of the TCC assembly within the torque converter
    Failed PCM/ECM/ECM

Note: This may well be an intermittent condition and may not reappear, so clear the code and continue monitoring.

Possible Solutions

You must first gather tools or borrow some (a rare phenomenon in mechanics because our tools are our livelihood and we don’t like lending our tools):

    On-board diagnostic tool (OBD-II) – to retrieve the code; can be found at many parts stores, online, or many parts stores pull the code for free
    Multimeter with resistance (or OHM) reading
    Self-powered test light/probe (a Power Probe III). If you don’t have a power probe, a simple set of fused jumper wires and a test light will suffice
    Wiring diagrams will be very helpful – you can get them in a Haynes manual or if you are friendly with the dealership or your local mechanic, they might be able to make a photocopy

TIP: Remember that in most cases, there is an internal transmission harness connecting the TCC solenoid and shift solenoids, so the wiring fault may only occur when the transmission is hot or cold. Or, when the vehicle is driven over bumps or during a turn. Make every effort to recreate it!

TIP: Before troubleshooting any transmission issue, ensure the engine is running perfectly! Address any other sensor codes or lean/rich codes first. There are many networked sensors that determine transmission shift programming. If one is “offline/faulty,” the ECM/PCM/ECM may trigger this code through the fault it sees on another sensor.

TIP: Many times, a simple fluid and filter change resolves minor transmission issues. There’s nothing to lose with a fluid and filter change.

Notice that I say change and not a fluid flush. A fluid flush on a high-mileage transmission can cause further damage. Also, for a slipping transmission, I recommend Lucas Oil Transmission Fix. I do not endorse the product and am not paid to use the name. But it works!

    First, verify the condition/concern. In most cases, the TCC solenoid applies in overdrive when commanded by the PCM. TCC lock-up helps fuel economy and lowers transmission fluid temperature because the converter is locked (look up TCC operation for an in-depth insight as theory and operation are difficult to explain without getting too technical. With this explanation, one might get the deer in the headlights look).
    In my case, my vehicle stumbled and nearly stalled at a light. Once verified, we can begin diagnosis.
    Perform a general condition check of the fluid and check the level if everything is OK. Also, is the transmission shifting properly? Is the engine running correctly? Most transmission problems are misdiagnosed due to poor engine performance. Remember, power flow starts at the engine and goes through the transmission, then to the drivetrain.
    Next, check the external transmission harness and connectors. Also check your fuses and ensure the transmission case is grounded AND connected to the battery.
    Proceed to locate the appropriate wires corresponding to the torque converter clutch. In most cases, this will be two wires; one for ground and one for positive. Apply power and ground and listen for the solenoid to click.
    If the solenoid does not click, proceed to check continuity through the solenoid and continuity to and from the corresponding wires to and from the sensor. The solenoid should have a low ohm reading (0.02 to 0.05), this will vary by manufacturer, so check your reading against a factory service manual or equivalent. The wires should also have a low ohm reading. Also ensure none of the wires are shorted to ground or power.
    If the wires check out and the solenoid clicks. There may be a PCM issue, but I advise pulling the transmission pan and carefully inspecting the TCC solenoid for debris. Any small amount of debris will cause the solenoid to short and make the computer think it is applied. Or, if it is metal debris, it will stick to the solenoid and prevent it from disengaging. This was the problem in my case.
    I would also advise getting the latest calibration for your vehicle’s computer (PCM) from your dealership. Manufacturers constantly release new, improved software. There may be a revised calibration to address this code. Especially if it is intermittent.
    Finally, if everything is OK and you go ahead and replace the PCM, remember it must be programmed for the vehicle. In many cases, there is an anti-theft device in the key and with that the keys need to be programmed. Think dealership or mechanic.
    If all else fails and you are at your wit’s end, there may be an issue with the clutch inside the torque converter. This will most likely be evident if you feel slipping when the transmission locks up in overdrive. The fluid may also smell burnt or be completely black.

Good luck! In my case, I am a Ford-trained technician and due to my experience, I simply pulled the transmission pan and took a look at the solenoid and found my problem right away. This is a common issue on higher-mileage transmissions.

P0744 Intermittent Torque Converter Clutch Circuit

What does it mean?

Modern vehicles equipped with automatic transmissions/transaxles use a torque converter between the engine and transmission to increase engine torque and drive the rear wheels.

The engine and transmission are actually connected by a fluid coupling mechanism inside the torque converter, which multiplies torque until the speeds equalize and create a “stall speed” where the difference between the actual engine speed and the transmission input speed is about 90% efficient. The Torque Converter Clutch (TCC) solenoids controlled by the Powertrain Control Module/Engine Control Module (PCM/ECM) or the Transmission Control Module (TCM) direct the hydraulic fluid and engage the torque converter clutch to create a solid coupling and increase efficiency.

The Transmission Control Module detected a malfunction in the circuit that operates the torque converter clutch solenoid.

Note: This code is similar to codes P0740, P0741, P0742, P0743, P2769, and P2770.

Symptoms

Symptoms of a P0744 trouble code may include:

Intermittent Malfunction Indicator Light (MIL) is on (e.g., check engine light)
Minimal decrease in fuel economy, this will not affect engine performance

Potential Causes

Causes

of this DTC may include:

Damaged transmission wiring harness, loose connection, or intermittent open/short circuit
Torque Converter Clutch (TCC) solenoid
Transmission Control Module (TCM)

Diagnostic Steps

for P0744 DTC

Wiring Harness – Check that the transmission wiring harness is not damaged or loose. Use a factory wiring diagram to locate the appropriate power source and all connection points between the circuits. The transmission may be powered by a fuse or relay and triggered by the TCM. Disconnect the transmission harness at the transmission connector, power source, and TCM. Check for a short to ground inside the internal transmission wiring harness by locating the appropriate + and – pins for the torque converter clutch solenoid.

Using a digital volt ohm meter (DVOM) set to an ohms scale, check for a short to ground in the circuit with the positive lead on one of the pins and the negative lead on a known good ground. If resistance is low, suspect a short to ground in the internal harness or TCC solenoid – removal of the transmission oil pan may be necessary to further diagnose the TCC solenoid.

Test the wiring between the TCM and the transmission case wiring harness connector using the DVOM set to ohms. Look for a possible short to ground by moving the DVOM’s negative lead to a known good ground; the resistance should be very high or above the limit (OL).

Test the control circuit wiring between the TCM and the wiring harness connector in the transmission case using the DVOM set to the volts scale – it may be necessary to remove the pin from each side of the harness connector to isolate it from the harness while it is still connected to the TCM and transmission case. With the positive lead at each end of the wiring and the negative lead on a known good ground, check for battery voltage with the key on/engine off. If voltage is present, suspect a short to power and determine the source of the short in the wiring harness.

Tip: Jiggling the wiring harness and connectors during testing can help locate an intermittent short to power or ground.

Torque Converter Clutch (TCC) Solenoid – Check the resistance of the TCC solenoid and internal transmission wiring to the transmission case after removing the transmission harness plug (if applicable, some makes/models use a TCM bolted directly to the transmission case). Some makes/models use a transmission wiring harness with the TCC solenoid and internal harness as a single unit. The DVOM should be set to an ohms scale with the positive and negative leads on the TCC power and control circuit pins. The resistance should be within the manufacturer’s specifications; if it is very high or above the limit (OL), remove the transmission oil pan to inspect the solenoid inside the transmission if possible.

Check for voltage on the power side of the TCC solenoid circuit with the key on/engine off and the harnesses connected or on the wiring harness connector at the TCM with the DVOM set to the volts scale, the positive lead on the control side of the solenoid and the negative on a known good ground with the vehicle key on/engine off; battery voltage should be present. Press on the solenoid and jiggle the wiring to determine if there is a short to power or ground.

Transmission Control Module (TCM) – Since the torque converter clutch is only activated under certain driving conditions, it will be necessary to monitor the TCM with an advanced scan tool to determine if the TCM is commanding the TCC Solenoid and what the actual feedback reading to the TCM is. The TCC solenoid is normally controlled by a duty cycle to achieve a smoother torque converter lockup engagement.

To test if the TCM is actually sending the signal, a graphing multimeter set to duty cycle or a digital storage oscilloscope will also be needed. The positive lead is probed into the wiring harness connected to the TCM and the negative lead to a known good ground. The duty cycle should match what is commanded by the TCM in the advanced scan tool reading. If the cycle is intermittent under hard road conditions, it may be a wiring issue. Check the connections again, and if all wiring/solenoid is in good condition or if road conditions do not coincide with intermittent readings, the TCM may be at fault.

Cadillac P1442 Code: EVAP System Leak Detection Pump Explained

Understanding the Cadillac P1442 Diagnostic Trouble Code

When your Cadillac’s check engine light illuminates and you retrieve the OBD2 code P1442, you’re dealing with a specific issue within the vehicle’s Evaporative Emission Control (EVAP) system. This code indicates a malfunction in the Leak Detection Pump (LDP) switch circuit, a critical component responsible for monitoring and maintaining the integrity of the fuel vapor containment system. The EVAP system prevents gasoline vapors from escaping into the atmosphere by storing them in a charcoal canister and periodically purging them into the engine for combustion.

What Does P1442 Mean Specifically?

P1442 is a manufacturer-specific code that primarily affects General Motors vehicles, including various Cadillac models. The technical definition is “Evaporative Emission (EVAP) System Leak Detection Pump Switch Circuit.” This means the vehicle’s Powertrain Control Module (PCM) has detected an electrical problem within the circuit that controls or monitors the leak detection pump’s switching mechanism. The PCM continuously monitors this circuit for proper voltage levels and signal patterns, and when it receives readings outside the expected parameters, it stores the P1442 code and illuminates the check engine light.

How the EVAP System and Leak Detection Pump Work

The EVAP system is a sealed network designed to capture and contain fuel vapors. The leak detection pump serves as the system’s diagnostic tool, performing self-tests to ensure there are no leaks that could release hydrocarbons into the atmosphere. During normal operation:

The LDP pressurizes the EVAP system with air
It monitors pressure decay rates to detect leaks
The pump contains a switch that signals its operational status to the PCM
This switch circuit is what triggers P1442 when malfunctioning

Common Symptoms of P1442 in Cadillac Vehicles

Recognizing the symptoms associated with code P1442 can help you address the issue promptly. While some drivers may not notice any drivability concerns, several indicators typically accompany this diagnostic trouble code.

Check Engine Light and Fuel Odor

The most immediate symptom is the illumination of the check engine light on your dashboard. Since the EVAP system deals with fuel vapors, you might also detect a faint gasoline smell around the vehicle, particularly near the fuel tank or engine compartment. This odor occurs because the system isn’t properly containing vapors, allowing them to escape into the surrounding air.

Failed Emissions Testing

In regions requiring periodic emissions testing, a vehicle with an active P1442 code will automatically fail inspection. The EVAP system is a critical component of your Cadillac’s emission control system, and any malfunction will result in test failure until the issue is resolved and the code is cleared.

Potential Fuel Economy Changes

While not always present, some drivers report slight decreases in fuel economy when P1442 is active. This occurs because the engine control module may enter a limited operational mode or because the fuel system isn’t operating at peak efficiency due to the EVAP system malfunction.

Primary Causes of P1442 Code in Cadillac Models

Diagnosing P1442 requires understanding the various components that could be responsible for triggering this code. The issue typically falls into one of several categories, ranging from simple electrical problems to component failures.

Electrical Circuit Issues

Since P1442 specifically references a “switch circuit,” electrical problems are among the most common causes:

Damaged or corroded wiring in the LDP circuit
Poor electrical connections at the LDP connector
Blown fuses affecting the EVAP system
Short circuits or open circuits in the wiring harness
Corroded grounds affecting circuit integrity

Leak Detection Pump Failure

The leak detection pump itself may be faulty. Internal mechanical failures, diaphragm damage, or electrical component failure within the pump can all trigger P1442. The pump contains a switch that signals its position to the PCM, and if this mechanism fails, it will set the code.

Other Potential Causes

While less common, several other issues can contribute to P1442:

Faulty PCM (rare, but possible)
Vacuum leaks in associated EVAP system lines
Problems with the EVAP canister vent valve
Physical damage to EVAP system components from road debris

Step-by-Step Diagnostic Procedure for P1442

Proper diagnosis of P1442 requires a systematic approach to identify the root cause efficiently. Following these steps can help pinpoint the issue without unnecessary parts replacement.

Initial Inspection and Visual Check

Begin with a thorough visual inspection of the EVAP system components:

Locate the leak detection pump (typically near the fuel tank or in the engine compartment)
Check for obvious physical damage to the LDP and wiring
Inspect electrical connectors for corrosion, bent pins, or poor engagement
Examine vacuum lines for cracks, disconnections, or deterioration
Verify all EVAP system components are properly mounted and secured

Electrical Circuit Testing

Using a digital multimeter, perform comprehensive electrical tests:

Check for power and ground at the LDP connector with ignition on
Test circuit resistance for opens or shorts
Verify signal voltage matches manufacturer specifications
Check for voltage drops across connections and wiring
Test related fuses and circuit protection devices

Component Function Testing

After verifying the electrical circuit is sound, test the LDP functionality:

Use a scan tool to activate the LDP and monitor its operation
Test pump diaphragm integrity using manufacturer-specific procedures
Verify the internal switch changes state during operation
Compare pump performance against factory specifications

Repair Procedures and Cost Considerations

Once diagnosis is complete, implementing the correct repair is essential for resolving P1442 permanently.

Common Repair Solutions

Depending on your diagnostic findings, repairs may include:

Replacing the leak detection pump assembly
Repairing or replacing damaged wiring and connectors
Cleaning corrosion from electrical connections
Replacing associated EVAP system components if needed
Addressing any vacuum leaks in related systems

Estimated Repair Costs

Repair costs for P1442 vary significantly based on the root cause and your Cadillac model:

Leak detection pump replacement: $150-$400 for parts plus 1-2 hours labor
Wiring repair: $100-$250 depending on complexity
Professional diagnosis: $80-$150 per hour
Total repair costs typically range from $200 to $600

Prevention and Maintenance Tips

Preventing recurrence of P1442 involves regular maintenance and careful driving habits. The EVAP system is particularly vulnerable to damage from impacts and environmental factors.

Regular EVAP System Maintenance

Implement these practices to maintain EVAP system health:

Have the system inspected during routine maintenance
Address any check engine lights promptly to prevent additional issues
Keep the area around EVAP components clean and free of debris
Ensure fuel cap is properly tightened after refueling
Follow manufacturer recommendations for EVAP system service intervals

Driving and Environmental Considerations

Certain conditions can increase the likelihood of EVAP system issues:

Avoid driving over rough terrain that could damage undercarriage components
Be cautious when parking in areas with tall grass or debris
In winter regions, rinse undercarriage regularly to remove road salt
Address even minor fuel smells immediately rather than ignoring them

Code P1442 in your Cadillac represents a specific electrical issue within the EVAP system’s leak detection pump circuit. While not typically an immediate drivability concern, it should be addressed promptly to maintain emission system integrity, ensure vehicle compliance, and prevent potential secondary issues. Proper diagnosis using a systematic approach will identify whether the issue lies with the LDP itself, its electrical circuit, or related components. With repair costs generally reasonable and prevention measures straightforward, resolving P1442 efficiently will restore your Cadillac’s emission system to proper operation and extinguish that check engine light.

P0745 Pressure Control Solenoid A Malfunction

What does it mean?

This is a generic diagnostic trouble code (DTC) and generally applies to OBD-II equipped vehicles with an automatic transmission.

This may include, but is not limited to, vehicles from Ford, Mercury, Lincoln, Jaguar, Chevrolet, Toyota, Nissan, Allison/Duramax, Dodge, Jeep, Honda, Acura, etc. Although generic, the exact repair steps may vary by year, make, model, and powertrain configuration.

When the OBD-II trouble code P0745 is set, the Powertrain Control Module (PCM) has detected a problem with the transmission pressure control solenoid “A”. Most automatic transmissions contain at least three solenoids which are solenoids A, B, and C. Trouble codes related to solenoid “A” are codes P0745, P0746, P0747, P0748, and P0749. The code set is based on the specific malfunction that alerts the PCM and illuminates the Check Engine light.

The purpose of transmission pressure control solenoids is to control fluid pressure for the proper operation of an automatic transmission. The PCM receives an electronic signal based on the pressure inside the solenoids. An automatic transmission is controlled by bands and clutches that shift gears by having fluid pressure in the right place at the right time. Based on signals from associated devices monitoring vehicle speed, the PCM commands the pressure solenoids to direct fluid at the appropriate pressure to various hydraulic circuits that change the transmission ratio at the correct time.

The P0745 code is set by the PCM when pressure control solenoid “A” experiences a general malfunction.

How severe is this DTC?

The severity of this code normally starts as moderate, but it can escalate to a more severe level quickly when not corrected in a timely manner.
What are some of the symptoms of the code?

Symptoms of a P0745 trouble code may include:

Vehicle enters limp mode
Transmission slips when shifting gears
Transmission overheating
Transmission shifts harshly
Reduced fuel economy

Symptoms

potentially misfiring
Check Engine light illuminated

What are some of the common causes of the code?

Causes

of this P0745 transmission code may include:

Faulty pressure control solenoid
Dirty or contaminated fluid
Dirty or clogged transmission filter
Faulty transmission pump
Faulty transmission valve body
Restricted hydraulic passages
Corroded or damaged connector
Faulty or damaged wiring
Faulty PCM

What are the troubleshooting steps for P0745?

Before starting the troubleshooting process for any malfunction, you should research Technical Service Bulletins (TSBs) for the specific vehicle by year, model, and transmission. In some circumstances, this can save you a lot of time in the long run by pointing you in the right direction. You should also check the vehicle records to verify the last time the filter and fluid were changed if possible.
Fluid and Wiring Inspections

The first step is to check the fluid level and examine the condition of the fluid for contamination. Before changing the fluid, you should check the vehicle records to verify the last time the filter and fluid were changed.

A detailed visual inspection to check the condition of the wiring for obvious defects is next. Check the connectors and connections for security, corrosion, and damaged pins. This should include all wiring and connectors for the transmission pressure control solenoids, transmission pump, and PCM. Depending on the configuration, the transmission pump may be electric or mechanical.
Advanced Steps

Advanced steps always become very vehicle-specific and require appropriate advanced equipment to perform accurately. These procedures require a digital multimeter and the vehicle-specific technical references. You must obtain the troubleshooting guidelines specific to your vehicle before proceeding with the advanced steps. Voltage requirements can be very specific to the particular vehicle model. Fluid pressure requirements will also vary depending on the transmission design and configuration.
Continuity Checks

Unless otherwise indicated in the technical data, normal readings for wiring and connections should be 0 ohms of resistance. Continuity checks should always be performed with the power disconnected from the circuit to avoid shorting the circuit and causing further damage. Resistance or lack of continuity is an indication of faulty wiring that is open or shorted and must be repaired or replaced.

P0746 Pressure Control Solenoid A Performance or Stuck Off

What does it mean?

This is a generic diagnostic trouble code (DTC) and generally applies to OBD-II equipped vehicles with an automatic transmission.

This can include, but is not limited to, vehicles from Ford, Mercury, Lincoln, Jaguar, Chevrolet, Toyota, Nissan, Allison/Duramax, Dodge, Jeep, Honda, Acura, etc. Although generic, the exact repair steps may vary by year, make, model, and powertrain configuration.

When the OBD-II trouble code P0746 is set, the Powertrain Control Module (PCM) has detected a problem with the transmission pressure control solenoid “A”. Most automatic transmissions contain at least three solenoids, which are solenoids A, B, and C. Trouble codes related to solenoid “A” are codes P0745, P0746, P0747, P0748, and P0749. The code set is based on the specific malfunction that alerts the PCM and illuminates the Check Engine light.

Transmission pressure control solenoids are designed to control fluid pressure for the proper operation of an automatic transmission. The PCM receives an electronic signal based on the pressure inside the solenoids. An automatic transmission is controlled by bands and clutches that shift gears by having fluid pressure in the right place at the right time. Based on signals from associated devices monitoring vehicle speed, the PCM commands the pressure solenoids to direct fluid at the appropriate pressure to various hydraulic circuits that change the gear ratio at the right time.

Code P0746 is set by the PCM when the pressure control solenoid “A” is not functioning correctly or is stuck in the “Off” position.

How severe is this DTC?

The severity of this code normally starts as moderate, but it can escalate to a more severe level quickly when not corrected in a timely manner.
What are some of the symptoms of the code?

Symptoms of a P0746 trouble code may include:

Vehicle enters limp mode
Transmission slips when shifting gears
Transmission overheating
Transmission shifts harshly
Reduced fuel economy

Symptoms

Potential misfires
Check Engine light illuminated

What are some of the common causes of the code?

Causes

of this P0746 transmission code may include:

What are the troubleshooting steps for P0746?

Before starting the troubleshooting process for any malfunction, you should research Technical Service Bulletins (TSBs) for the specific vehicle by year, model, and transmission. In some circumstances, this can save you a lot of time in the long run by pointing you in the right direction. You should also check the vehicle’s records to verify the last time the filter and fluid were changed if possible.
Fluid and Wiring Inspections

The first step is to check the fluid level and examine the condition of the fluid for contamination. Before changing the fluid, you should check the vehicle’s records to verify the last time the filter and fluid were changed.

Advanced steps always become very vehicle-specific and require appropriate advanced equipment to perform accurately. These procedures require a digital multimeter and the vehicle-specific technical references. You must obtain the troubleshooting guidelines specific to your vehicle before proceeding with the advanced steps. Voltage requirements can be very specific to the vehicle model. Fluid pressure requirements will also vary depending on the transmission design and configuration.
Continuity Checks

Unless otherwise indicated in the technical data, normal readings for wiring and connections should be 0 ohms of resistance. Continuity checks should always be performed with the power disconnected from the circuit to avoid shorting the circuit and causing more damage. Resistance or lack of continuity is an indication of faulty wiring that is open or shorted and must be repaired or replaced.
What are the common repairs for this code?

Replacing the fluid and filter
Replacing the faulty pressure control solenoid
Repairing or replacing a faulty transmission pump
Repairing or replacing the faulty transmission valve body
Flushing the transmission to clean the passages
Cleaning corrosion from connectors
Repairing or replacing the wiring
Replacing the PCM

Possible misdiagnosis may include:

Engine misfire problem
Transmission pump problem
Internal transmission problem
Transmission problem

I hope the information in this article has helped point you in the right direction to correct the issue with your pressure control solenoid trouble code. This article is strictly informational, and the technical data and service bulletins specific to your vehicle should always take priority.

P0747 Pressure Control Solenoid A Stuck

What Does It Mean?

This is a generic diagnostic trouble code (DTC) and generally applies to OBD-II equipped vehicles with an automatic transmission.

This can include, but is not limited to, vehicles from Ford, Mercury, Lincoln, Jaguar, Chevrolet, Toyota, Nissan, Allison/Duramax, Dodge, Jeep, Honda, Acura, etc. Although generic, the exact repair steps may vary depending on the year, make, model, and powertrain configuration.

When the OBD-II fault code P0747 is set, the Powertrain Control Module (PCM) has detected a problem with the transmission pressure control solenoid “A”. Most automatic transmissions contain at least three solenoids, which are solenoids A, B, and C. Fault codes related to solenoid “A” are codes P0745, P0746, P0747, P0748, and P0749. The specific code set is based on the particular malfunction that alerts the PCM and illuminates the Check Engine light.

The purpose of the transmission pressure control solenoids is to control fluid pressure for the proper operation of an automatic transmission. The PCM receives an electronic signal based on the pressure inside the solenoids. An automatic transmission is controlled by bands and clutches that shift gears by having fluid pressure in the right place at the right time. Based on signals from associated devices monitoring vehicle speed, the PCM commands the pressure solenoids to direct fluid at the appropriate pressure to various hydraulic circuits that change the gear ratio at the correct time.

Code P0747 is set by the PCM when pressure control solenoid “A” is stuck in the “On” position.

How severe is this DTC?

The severity of this code normally starts as moderate, but it can escalate to a more severe level quickly if not corrected in a timely manner.
What are some of the symptoms of the code?

Symptoms of a P0747 fault code may include:

Vehicle enters limp mode
Transmission slips when shifting gears
Transmission overheating
Transmission shifts harshly
Reduced fuel economy

Symptoms

Potential misfires
Check Engine light illuminated

What are some common causes of the code?

Causes

of this P0747 transmission code may include:

What are the troubleshooting steps for P0747?

Before starting the troubleshooting process for any malfunction, you should research Technical Service Bulletins (TSBs) for the specific vehicle by year, model, and transmission. In some circumstances, this can save you a lot of time in the long run by pointing you in the right direction. You should also check the vehicle’s records to verify the last time the filter and fluid were changed, if possible.
Fluid and Wiring Inspections

A detailed visual inspection to check the condition of the wiring for obvious defects is next. Check the connectors and connections for security, corrosion, and damaged pins. This should include all wiring and connectors for the transmission pressure control solenoids, the transmission pump, and the PCM. Depending on the configuration, the transmission pump may be electric or mechanical.
Advanced Steps

Unless otherwise indicated in the technical data, normal readings for wiring and connections should be 0 ohms of resistance. Continuity checks should always be performed with the power disconnected from the circuit to avoid shorting the circuit and causing further damage. Resistance or lack of continuity indicates faulty wiring that is open or shorted and must be repaired or replaced.
What are the common repairs for this code?

Repairing or replacing wiring
Flashing or replacing the PCM

Possible misdiagnosis may include:

Engine misfire problem
Transmission pump problem
Internal transmission problem
Transmission problem

I hope the information in this article has helped point you in the right direction to correct the issue with your pressure control solenoid fault code. This article is strictly informational, and the technical data and service bulletins specific to your vehicle should always take priority.

Pressure Control Solenoid A

What Does It Mean?

This is a generic diagnostic trouble code (DTC) and generally applies to OBD-II equipped vehicles with an automatic transmission.

This may include, but is not limited to, vehicles from Ford, Mercury, Lincoln, Jaguar, Chevrolet, Toyota, Nissan, Allison/Duramax, Dodge, Jeep, Honda, Acura, etc. Although generic, the exact repair steps may vary depending on the year, make, model, and powertrain configuration.

When the OBD-II trouble code P0748 is set, the Powertrain Control Module (PCM) has detected a problem with the transmission pressure control solenoid “A”. Most automatic transmissions contain at least three solenoids, which are solenoids A, B, and C. The trouble codes related to solenoid “A” are codes P0745, P0746, P0747, P0748, and P0749. The set of codes is based on the specific malfunction that alerts the PCM and illuminates the Check Engine light.

The P0748 code is set by the PCM when the pressure control solenoid “A” experiences an electrical malfunction.

How Severe Is This DTC?

The severity of this code normally starts as moderate, but it can escalate to a more severe level quickly when not corrected in a timely manner.
What Are Some of the Symptoms of the Code?

Symptoms of a P0748 trouble code may include:

Vehicle enters limp mode
Transmission slips when shifting gears
Transmission overheating
Transmission shifts harshly
Reduced fuel economy

Symptoms

Potential misfires
Check Engine light illuminated

What Are Some of the Common Causes of the Code?

Causes

of this P0748 transmission code may include:

What Are the Troubleshooting Steps for P0748?

Before starting the troubleshooting process for any malfunction, you should research the Technical Service Bulletins (TSBs) for the specific vehicle by year, model, and transmission. In some circumstances, this can save you a lot of time in the long run by pointing you in the right direction. You should also check the vehicle’s records to verify the last time the filter and fluid were changed if possible.
Fluid and Wiring Inspections

Replacing the fluid and filter
Replacing the faulty pressure control solenoid
Repairing or replacing a faulty transmission pump
Repairing or replacing the faulty transmission valve body
Flushing the transmission to clean the passages
Cleaning corroded connectors
Repairing or replacing the wiring
Replacing the PCM

Possible misdiagnosis may include:

Engine misfire issue
Transmission pump problem
Internal transmission problem
Transmission issue

Buick P1442 Code: EVAP System Leak Detection Explained

Understanding the Buick P1442 OBD2 Diagnostic Code

The P1442 diagnostic trouble code is a manufacturer-specific code that primarily affects General Motors vehicles, including various Buick models. This code indicates a malfunction within the Evaporative Emission Control (EVAP) system, specifically related to the leak detection pump circuit. When your Buick’s powertrain control module (PCM) detects an irregularity in the leak detection pump’s operation or circuit, it stores code P1442 and illuminates the check engine light.

What Does P1442 Mean for Your Buick?

P1442 specifically points to a problem with the leak detection pump control circuit. The EVAP system is designed to prevent fuel vapors from escaping into the atmosphere, and the leak detection pump is crucial for monitoring system integrity. When this code appears, it means your vehicle’s computer has detected an electrical or functional issue with this component, potentially compromising the entire emissions control system.

Buick Models Commonly Affected by P1442

While P1442 can potentially affect any Buick vehicle, it’s most frequently reported in popular models including:

Buick Enclave
Buick LaCrosse
Buick Regal
Buick Lucerne
Buick Verano
Buick Encore

Primary Causes of P1442 in Buick Vehicles

Diagnosing the root cause of P1442 requires systematic troubleshooting. The issue can range from simple electrical problems to complex mechanical failures within the EVAP system.

Electrical Circuit Failures

Electrical issues are among the most common causes of P1442 codes in Buick vehicles. These may include:

Damaged wiring harnesses or connectors to the leak detection pump
Corroded electrical terminals causing poor connectivity
Blown fuses in the EVAP system circuit
Faulty relay operation affecting pump power supply
Voltage drops or shorts in the control circuit

Mechanical Component Failures

Physical component failures can also trigger the P1442 code. Key mechanical issues include:

Failed leak detection pump motor or mechanism
Cracked or damaged vacuum lines in the EVAP system
Faulty purge valve operation affecting system pressure
Damaged EVAP canister affecting overall system function
Worn pump diaphragm reducing detection capability

Control Module and Sensor Issues

Sometimes the problem originates from the controlling systems rather than the physical components:

Malfunctioning powertrain control module (PCM)
Faulty pressure sensors within the EVAP system
Software glitches in the vehicle’s emission control system
Communication errors between modules

Symptoms and Diagnostic Procedures for P1442

Recognizing the symptoms and following proper diagnostic procedures is essential for accurate repair of P1442 code issues in Buick vehicles.

Common Symptoms of P1442 Code

When P1442 appears in your Buick, you may notice several telltale signs:

Illuminated check engine light on the dashboard
Possible fuel odor around the vehicle
Reduced fuel efficiency over time
Failed emissions testing during inspection
Rough engine idle in some cases
Difficulty starting the engine in rare instances

Professional Diagnostic Approach

Technicians follow a systematic approach to diagnose P1442 accurately:

Begin with comprehensive code scan and freeze frame data analysis
Perform visual inspection of EVAP system components and wiring
Test leak detection pump electrical circuits for proper voltage
Check for vacuum leaks using smoke machine testing
Verify proper operation of related sensors and valves
Conduct functional tests of the leak detection pump

Repair Procedures and Solutions for P1442

Addressing P1442 requires methodical repair approaches. The complexity of repairs varies depending on the root cause identified during diagnostics.

Electrical System Repairs

When electrical issues cause P1442, repairs typically involve:

Repairing or replacing damaged wiring harness sections
Cleaning or replacing corroded electrical connectors
Replacing blown fuses in the EVAP circuit
Testing and replacing faulty relays
Ensuring proper grounding connections

Component Replacement Procedures

Mechanical component failures require specific replacement procedures:

Leak detection pump replacement following manufacturer guidelines
EVAP canister replacement when contamination occurs
Purge valve replacement to restore proper system operation
Vacuum line replacement using OEM-quality components
Proper system calibration after component replacement

Post-Repair Verification and Testing

After completing repairs, thorough verification is crucial:

Clear diagnostic codes and perform drive cycle completion
Monitor system operation for code recurrence
Verify EVAP system holds proper vacuum during testing
Confirm check engine light remains off during normal operation
Document repair procedures for future reference

Preventive Maintenance and Long-Term Solutions

Preventing recurrence of P1442 involves regular maintenance and awareness of potential issues before they become major problems.

Regular EVAP System Maintenance

Maintaining your Buick’s EVAP system can prevent P1442 and related codes:

Schedule regular emissions system inspections
Address check engine lights promptly to prevent additional damage
Ensure proper fuel cap installation and replacement
Keep electrical connections clean and protected from moisture
Follow manufacturer-recommended service intervals

Professional vs. DIY Repair Considerations

Understanding when to seek professional help is important for P1442 repairs:

Simple electrical repairs may be suitable for experienced DIYers
Complex component replacements often require professional tools
Smoke testing and specialized diagnostics need professional equipment
Warranty considerations may affect repair decisions
Proper system calibration requires professional expertise

Addressing P1442 promptly in your Buick ensures optimal vehicle performance, maintains emission compliance, and prevents potential damage to other engine components. Regular maintenance and professional diagnostics when needed will keep your EVAP system functioning properly for years to come.

P0749 Pressure Control Solenoid A Intermittent

What Does It Mean?

This is a generic diagnostic trouble code (DTC) and generally applies to OBD-II equipped vehicles with an automatic transmission.

When the OBD-II fault code P0749 is set, the Powertrain Control Module (PCM) has detected a problem with the transmission pressure control solenoid “A”. Most automatic transmissions contain at least three solenoids, which are solenoids A, B, and C. Fault codes related to solenoid “A” are codes P0745, P0746, P0747, P0748, and P0749. The code set is based on the specific malfunction that alerts the PCM and illuminates the Check Engine light.

Code P0749 is set by the PCM when the pressure control solenoid “A” is operating intermittently.

How Severe Is This DTC?

The severity of this code normally starts as moderate, but it can escalate to a more severe level quickly if not corrected in a timely manner.
What Are Some of the Symptoms of the Code?

Symptoms of a P0749 fault code may include:

Vehicle enters limp mode
Transmission slips when shifting gears
Transmission overheating
Transmission shifts harshly
Reduced fuel economy

Symptoms

potential misfires
Check Engine light illuminated

What Are Some of the Common Causes of the Code?

Causes

of this P0749 transmission code may include:

What Are the Troubleshooting Steps for P0749?

Before starting the troubleshooting process for any malfunction, you should research Technical Service Bulletins (TSBs) for the specific vehicle by year, model, and transmission. In some circumstances, this can save you a lot of time in the long run by pointing you in the right direction. You should also check the vehicle’s records to verify the last time the filter and fluid were changed if possible.
Fluid and Wiring Inspections

A detailed visual inspection to check the condition of the wiring for obvious defects is next. Check connectors and connections for security, corrosion, and damaged pins. This should include all wiring and connectors for the transmission pressure control solenoids, transmission pump, and PCM. Depending on the configuration, the transmission pump may be electric or mechanical.
Advanced Steps

Advanced steps always become very vehicle-specific and require appropriate advanced equipment to perform accurately. These procedures require a digital multimeter and the vehicle-specific technical references. You must obtain the troubleshooting guidelines specific to your vehicle before proceeding with advanced steps. Voltage requirements can be very specific to the particular vehicle model. Fluid pressure requirements will also vary depending on the transmission’s design and configuration.
Continuity Checks

Unless otherwise indicated in the technical data, normal readings for wiring and connections should be 0 ohms of resistance. Continuity checks should always be performed with the power disconnected from the circuit to avoid short-circuiting and causing further damage. Resistance or lack of continuity indicates faulty wiring that is open or shorted and must be repaired or replaced.
What are the common repairs for this code?

Replacing fluid and filter
Replacing the faulty pressure control solenoid
Repairing or replacing a faulty transmission pump
Repairing or replacing the faulty transmission valve body
Flushing the transmission to clean passages
Cleaning corrosion from connectors

Repairing or replacing wiring
Replacing PCM

Possible misdiagnosis may include:

Engine misfire issue
Transmission pump problem
Internal transmission problem
Transmission issue