P0732 Incorrect Speed 2 Report

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.

This code may appear in vehicles with an automatic transmission when there is an issue shifting into 2nd gear, or while driving in 2nd gear. The computer-controlled automatic transmission uses multiple gears to increase vehicle speed while maximizing engine power output. Newer vehicles may have more than four gears to improve fuel economy. The computer determines when to upshift or downshift between gears based on throttle position relative to vehicle speed.

The Engine Control Module (ECM), Powertrain Control Module (PCM), or Transmission Control Module (TCM) uses inputs from various sensors to verify proper transmission and component operation. Engine speed is often calculated relative to the transmission speed sensor to determine gear ratio and torque converter slippage. If the calculation doesn’t match the desired value, a diagnostic code is set and the Check Engine light is illuminated. Incorrect ratio codes typically require advanced mechanical capability and diagnostic tools.

Note: This code is similar to P0730, P0730, P0731, P0733, P0734, P0735 and P0736. If other transmission codes exist, repair those issues before proceeding with an incorrect gear ratio code.

Symptoms

Symptoms of a P0732 trouble code may include:

Illuminated check engine light (malfunction indicator)
Delayed or no shift into 2nd gear
Transmission slipping
Loss of fuel economy
Potential causes

Causes

of this DTC may include:

Low or dirty transmission fluid
Mechanical failure inside the transmission
Internal blockage within the transmission main control
Faulty shift solenoid
Faulty transmission control module

Diagnostic steps

Always ensure to check the fluid level and condition before proceeding with diagnosis. Incorrect fluid level or dirty fluid can cause shifting problems affecting multiple gears. If only one incorrect ratio code is displayed, test drive the vehicle to determine if the gear is actually functioning.

Transmission internal clutches and bands are typically controlled by a solenoid or using fluid pressure. If there’s an electrical issue with a shift solenoid, a code specific to that fault should also be displayed. Address the electrical issue before proceeding. Blocked fluid passages inside the transmission can also prevent the vehicle from shifting into 2nd gear. If there are multiple incorrect ratio codes but the transmission operates as expected, there might be a mechanical issue with the torque converter, transmission main control, or pressure problems.

If there are multiple incorrect ratio codes and shifting problems, but not all are displayed, the fault could be an internal mechanical problem within the transmission, or fluid pressure/blocked passages in the main control. A shift solenoid controlling multiple gears could also be responsible in case of internal blockage or fluid pressure issues. If there’s an electrical problem with the solenoid controlling the gears, a code should be displayed specific to the faulty solenoid.

It may be necessary to use an advanced diagnostic scan tool to determine which gear is being commanded by the transmission and to determine if engine speed matches the calculated output speed from the transmission sensor.

Thorough knowledge of transmission operation and overhaul is often required to repair this type of malfunction. Consult the factory service manual for vehicle-specific diagnostic procedures.

P0733 Incorrect Speed Ratio 3

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.

This code may appear in vehicles with automatic transmissions when there is an issue shifting into 3rd gear or driving in 3rd gear. The computer-controlled automatic transmission uses multiple gears to increase vehicle speed while maximizing engine power output. Newer vehicles may have more than four gears to improve fuel economy. The computer determines when to upshift or downshift between gears based on throttle position relative to vehicle speed.

The Engine Control Module (ECM), Powertrain Control Module (PCM), or Transmission Control Module (TCM) uses inputs from various sensors to verify proper transmission operation and its components. Engine speed is often calculated relative to the transmission speed sensor to determine gear ratio and torque converter slippage. If the calculation does not match the desired value, a diagnostic code is set and the Check Engine light is illuminated. Incorrect ratio codes typically require advanced mechanical capability and diagnostic tools.

Note: This code is similar to P0730, P0730, P0731, P0732, P0734, P0735 and P0736. If there are other transmission codes, repair those issues before proceeding with an incorrect gear ratio code.

Symptoms

Symptoms of a P0733 trouble code may include:

Engine light illuminated (malfunction indicator)
Delayed shifting or no shift into 3rd gear
Transmission slipping
Loss of fuel economy
Potential causes

Causes

of this DTC may include:

Low or dirty transmission fluid
Mechanical failure inside the transmission
Internal blockage within the main transmission control
Faulty shift solenoid
Faulty transmission control module

Diagnostic

and repair steps

Always ensure to check the fluid level and condition before proceeding with diagnosis. Incorrect fluid level or dirty fluid can cause shifting problems that affect multiple gears. If only one incorrect ratio code is displayed, test drive the vehicle to determine if the gear is actually functioning.

Transmission internal clutches and bands are typically controlled by a solenoid or using fluid pressure. If there is an electrical problem with a shift solenoid, a code specific to that fault should also be displayed. Correct the electrical issue before proceeding. Blocked fluid passages inside the transmission can also prevent the vehicle from shifting into 3rd gear. If there are multiple incorrect ratio codes but the transmission operates as expected, there might be a mechanical problem with the torque converter, main transmission control, or pressure issues.

If there are multiple incorrect ratio codes and shifting problems, but not all are displayed, the fault may be an internal mechanical problem within the transmission, or fluid pressure/blocked passages in the main control. A shift solenoid that controls multiple gears could also be responsible in case of internal blockage or fluid pressure problems. If there is an electrical problem with the solenoid controlling the gears, a code should be displayed specific to the faulty solenoid.

Thorough knowledge of transmission operation and overhaul is often required to repair this type of malfunction. Consult the factory service manual for vehicle-specific diagnostic procedures.

P0734 Incorrect Speed 4 Report

What does it mean?

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

This code may appear in vehicles with an automatic transmission when there is an issue shifting into 4th gear or while driving in 4th gear. The computer-controlled automatic transmission uses multiple gears to increase vehicle speed while maximizing engine power output. Newer vehicles may have more than four gears to improve fuel economy. The computer determines when to upshift or downshift between gears based on throttle position relative to vehicle speed.

The Engine Control Module (ECM), Powertrain Control Module (PCM), or Transmission Control Module (TCM) uses inputs from various sensors to verify proper transmission and component operation. Engine speed is often calculated relative to the transmission speed sensor to determine gear ratio and torque converter slippage. If the calculation does not match the desired value, a diagnostic code is set and the Check Engine light is illuminated. Incorrect ratio codes typically require advanced mechanical capability and diagnostic tools.

Note: This code is similar to P0730, P0731, P0732, P0733, P0735, and P0736. If other transmission codes exist, repair those issues before proceeding with an incorrect gear ratio code.

Symptoms

Symptoms of a P0734 trouble code may include:

Illuminated check engine light (malfunction indicator)
Delayed or no shift into 4th gear
Transmission slipping
Reduced fuel economy

Potential Causes

Causes of this DTC may include:

Low or dirty transmission fluid
Mechanical failure inside the transmission
Internal blockage within the main transmission control
Faulty shift solenoid
Faulty transmission control module

Diagnostic and Repair Steps

Transmission internal clutches and bands are typically controlled by a solenoid or using fluid pressure. If there’s an electrical issue with a shift solenoid, a specific fault code for that should also be displayed. Address the electrical issue before proceeding. Blocked fluid passages inside the transmission can also prevent the vehicle from shifting into 4th gear. If multiple incorrect ratio codes exist but the transmission operates as expected, there might be a mechanical issue with the torque converter, main transmission control, or pressure problems.

If there are multiple incorrect ratio codes and shifting problems, but not all are displayed, the fault could be an internal mechanical problem within the transmission, or fluid pressure/blocked passages in the main control. A shift solenoid controlling multiple gears could also be responsible in case of internal blockage or fluid pressure issues. If there’s an electrical problem with the solenoid controlling the gears, a code specific to the faulty solenoid should be displayed.

Comprehensive knowledge of transmission operation and overhaul is often required to repair this type of malfunction. Consult the factory service manual for vehicle-specific diagnostic procedures.

Honda P1442 Code: EVAP System Control Valve Malfunction

Understanding the Honda P1442 Diagnostic Trouble Code

The P1442 diagnostic trouble code is a manufacturer-specific code primarily associated with Honda and Acura vehicles. This code indicates a malfunction within the Evaporative Emission Control (EVAP) system, specifically related to the EVAP system control valve circuit. When this code appears, your vehicle’s Powertrain Control Module (PCM) has detected an electrical or functional problem with the valve responsible for managing fuel vapor flow from the EVAP canister.

What Does the P1442 Code Mean?

P1442 specifically points to an issue with the EVAP system control valve, which is part of the vehicle’s secondary air injection system on many Honda models. This valve plays a crucial role in controlling the flow of fuel vapors from the charcoal canister to the intake manifold, preventing them from escaping into the atmosphere while ensuring optimal engine performance.

How the EVAP System Control Valve Operates

The EVAP system control valve is an electrically operated solenoid valve that opens and closes based on signals from the PCM. During specific engine operating conditions, the PCM energizes the valve to allow stored fuel vapors from the charcoal canister to be drawn into the intake manifold and burned during combustion. This process helps reduce hydrocarbon emissions and improves fuel efficiency.

Common Symptoms of a P1442 Code

When the P1442 code is stored in your Honda’s PCM, you may experience various symptoms that indicate a problem with the EVAP system control valve. Recognizing these symptoms early can prevent more serious issues and potential emission test failures.

Check Engine Light Illumination

The most immediate and common symptom of a P1442 code is the illumination of the check engine light on your dashboard. While the vehicle may still operate normally initially, ignoring this warning can lead to more significant problems over time.

Fuel Odor and Emission Issues

Since the EVAP system contains fuel vapors, a malfunctioning control valve may cause a noticeable fuel smell around the vehicle, particularly near the fuel tank or engine compartment. You might also experience increased hydrocarbon emissions during emission testing.

Potential Performance Concerns

While not always immediately apparent, a persistent P1442 code can eventually lead to minor drivability issues such as:

Rough idling in some conditions
Slight decrease in fuel efficiency
Difficulty passing emission tests
Possible issues with engine starting in rare cases

Primary Causes of the P1442 Code

Diagnosing the root cause of a P1442 code requires systematic troubleshooting. Several components and systems can contribute to this diagnostic trouble code appearing in your Honda’s PCM.

Faulty EVAP System Control Valve

The most direct cause of a P1442 code is a malfunctioning EVAP system control valve itself. This valve can fail due to electrical issues, mechanical binding, or internal component wear. Common valve failures include:

Electrical short circuits or open circuits in the valve solenoid
Stuck valve mechanism preventing proper operation
Internal corrosion or contamination from fuel vapors
Physical damage to the valve housing or connectors

Electrical Circuit Problems

Since the EVAP system control valve is electrically operated, issues within its circuit can trigger the P1442 code. These electrical problems may include:

Damaged or corroded wiring harness connectors
Short to ground or short to power in control circuits
Open circuits in the power or ground supply wires
Poor electrical connections at the valve or PCM

Vacuum Line and Hose Issues

The EVAP system control valve relies on vacuum lines to function properly. Problems with these components can mimic valve failure and trigger the P1442 code:

Cracked, disconnected, or leaking vacuum hoses
Blocked or restricted vacuum lines
Improper hose routing during previous repairs
Degraded hose material causing vacuum leaks

Diagnostic and Repair Procedures for P1442

Proper diagnosis of a P1442 code requires a systematic approach using appropriate tools and following manufacturer-recommended procedures. Always consult your vehicle’s specific service manual for detailed instructions.

Initial Diagnostic Steps

Begin your diagnosis with these preliminary checks:

Verify the code with an OBD2 scanner and check for additional codes
Perform a visual inspection of the EVAP system control valve and associated components
Check all electrical connections for corrosion, damage, or looseness
Inspect vacuum lines for cracks, disconnections, or obvious damage
Listen for unusual sounds from the valve during key-on-engine-off tests

Electrical Circuit Testing

Using a digital multimeter, perform these electrical tests:

Check power supply to the valve with ignition ON
Test ground circuit integrity
Measure valve solenoid resistance and compare to specifications
Check for short circuits between wires
Verify PCM output signals using a scan tool or oscilloscope

Component Replacement and System Verification

After identifying the faulty component, proceed with replacement:

Disconnect the battery negative terminal before beginning work
Remove the old EVAP system control valve following service manual procedures
Install the new valve using proper torque specifications
Reconnect all electrical and vacuum connections securely
Clear the trouble codes and perform a system test drive
Verify repair success by ensuring the check engine light remains off

Preventive Maintenance and Long-Term Solutions

Preventing recurrence of the P1442 code involves regular maintenance and addressing underlying issues that may contribute to EVAP system component failure.

Regular EVAP System Inspection

Incorporate these checks into your regular maintenance routine:

Periodically inspect EVAP system components during oil changes
Check vacuum lines for brittleness or cracking, especially in older vehicles
Ensure the gas cap is properly tightened after refueling
Address any fuel system issues promptly to prevent contamination

Using Quality Replacement Parts

When replacement is necessary, always use quality components:

Choose OEM or OEM-equivalent replacement parts
Avoid cheap aftermarket components that may not meet specifications
Ensure proper part numbers for your specific Honda model and year
Consider replacing related components if they show signs of wear

Successfully diagnosing and repairing a P1442 code requires understanding the EVAP system’s operation and following proper diagnostic procedures. While this repair is often straightforward, complex electrical issues may require professional assistance. Regular maintenance and prompt attention to check engine lights can prevent more serious problems and ensure your Honda continues to operate efficiently while meeting emission standards.

Incorrect Speed 5 Report

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.

This code may appear in vehicles with an automatic transmission when there is an issue shifting into 5th gear, or while driving in 5th gear. The computer-controlled automatic transmission uses multiple gears to increase vehicle speed while maximizing engine output power. Newer vehicles may have more than four gears to improve fuel economy. The computer determines when to upshift or downshift between gears based on throttle position relative to vehicle speed.

The Engine Control Module (ECM), Powertrain Control Module (PCM), or Transmission Control Module (TCM) uses inputs from various sensors to verify proper transmission and component operation. Engine speed is often calculated relative to the transmission speed sensor to determine gear ratio and torque converter slippage. If the calculation does not match the desired value, a diagnostic code is set and the Check Engine light is illuminated. Incorrect ratio codes typically require advanced mechanical capability and diagnostic tools.

Note: This code is similar to P0730, P0731, P0732, P0733, P0734, and P0736. If other transmission codes exist, repair those issues before proceeding with an incorrect gear ratio code.

Symptoms

Symptoms of a P0735 trouble code may include:

Check Engine light illuminated (malfunction indicator)
Delayed or no shift into 5th gear
Transmission slipping
Loss of fuel economy

Potential Causes

Causes

of this DTC may include:

Low or dirty transmission fluid
Mechanical failure inside transmission
Internal blockage within main transmission control
Faulty shift solenoid
Defective transmission control module

Diagnostic

and Repair Steps

Always ensure to check fluid level and condition before proceeding with diagnosis. Incorrect fluid level or dirty fluid can cause shifting problems affecting multiple gears. If only one incorrect ratio code is displayed, test drive the vehicle to determine if the gear is actually functioning.

Transmission internal clutches and bands are typically controlled by a solenoid or using fluid pressure. If there is an electrical problem with a shift solenoid, a code specific to that fault should also be displayed. Correct the electrical issue before proceeding. Blocked fluid passage inside the transmission can also prevent the vehicle from shifting into 5th gear. If multiple incorrect ratio codes exist but the transmission operates as expected, there might be a mechanical problem with the torque converter, main transmission control, or pressure issues.

If there are multiple incorrect ratio codes and shifting problems, but not all are displayed, the fault could be an internal mechanical problem within the transmission, or fluid pressure/blocked passage in the main control. A shift solenoid controlling multiple gears could also be responsible in case of internal blockage or fluid pressure problem. If there is an electrical problem with the solenoid controlling the gears, a code should be displayed specific to the faulty solenoid.

Thorough knowledge of transmission operation and overhaul is often required to repair this type of malfunction. Consult the factory service manual for vehicle-specific diagnostic procedures.

P0736 Incorrect Reverse Gear Report

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.

This code may appear in vehicles with automatic transmissions when there is a problem shifting into reverse or while in reverse. The automatic transmission changes the output direction to move the vehicle in reverse and is most often manually controlled by hydraulic pressure, even in computer-controlled transmissions.

The Engine Control Module (ECM), Powertrain Control Module (PCM), or Transmission Control Module (TCM) uses inputs from various sensors to verify the proper operation of the transmission and its components. Engine speed is often calculated relative to the transmission speed sensor to determine the gear ratio and torque converter slip. If the calculation does not match the desired value, a diagnostic code is set and the Check Engine light is illuminated. Incorrect ratio codes typically require advanced mechanical skills and diagnostic tools.

Note: This code is similar to P0730, P0730, P0731, P0732, P0733, P0734, and P0735. If there are other transmission codes, repair those issues before proceeding with an incorrect gear ratio code.

Symptoms

Symptoms of a P0736 trouble code may include:

Check Engine light illuminated (malfunction indicator)
Delayed or no shift into reverse
Transmission slipping

Potential Causes

Causes

of this DTC may include:

Low or dirty transmission fluid
Mechanical failure inside the transmission
Internal blockage within the transmission main control
Faulty shift solenoid
Faulty transmission control module

Diagnostic

/ repair steps

Always ensure to check the fluid level and condition before proceeding with diagnosis. Incorrect fluid level or dirty fluid can cause shifting problems affecting multiple gears. If only one incorrect ratio code is displayed, test the vehicle to determine if the gear is actually functioning.

Transmission internal clutches and bands are typically controlled by a solenoid or using fluid pressure. If there is an electrical issue with a shift solenoid, a code specific to that fault should also be displayed. Fix the electrical issue before proceeding. Blocked fluid passages inside the transmission can also prevent the vehicle from shifting into reverse; if there are multiple incorrect ratio codes but the transmission operates as expected, there might be a mechanical issue with the torque converter, transmission main control, or pressure problems.

If there are multiple incorrect ratio codes and shifting issues, but not all are displayed, the fault could be an internal mechanical problem within the transmission, or fluid pressure/blocked passages in the main control. A shift solenoid controlling multiple gears could also be at fault in case of internal blockage or fluid pressure issues. If there is an electrical issue with the solenoid controlling the gears, a code should be displayed specific to the faulty solenoid.

Reverse gear in the transmission is generally not controlled by a solenoid; it is entirely hydraulic. If the transmission does not shift into reverse, there is most likely a mechanical or pressure issue causing the problem.

It may be necessary to use an advanced diagnostic scan tool to determine which gear is commanded by the transmission and to verify if the engine speed matches the calculated output speed from the transmission sensor.

In-depth knowledge of transmission operation and overhaul is often required to repair this type of malfunction. Consult the factory service manual for vehicle-specific diagnostic procedures.

P0737 Engine Speed Output Circuit TCM

What Does It Mean?

This is a generic powertrain diagnostic trouble code (DTC) that applies to OBD-II vehicles. This may include, but is not limited to, Dodge, Chevrolet, Honda, Toyota, Hyundai, Jaguar vehicles, etc. Although generic, the exact repair steps may vary depending on the year, make, model, and powertrain configuration.

The TCM (Transmission Control Module) operates similarly to the ECM (Engine Control Module) in that it monitors, controls, and regulates transmission functions while the ECM does the same for the engine.

The TCM uses various sensors and switches along with the ECM to monitor, control, and regulate transmission operation. Specifically, the TCM uses an engine speed sensor (ESS) to determine shift points among other functions. As its name suggests, the ESS monitors engine speed. Other names for the ESS may include CKP (crankshaft position sensor) or OSS (output speed sensor).

Most of the time, it measures crankshaft speed using a Hall effect-type sensor. The sensor uses notches in the flywheel that pass through the sensor to monitor crankshaft position. It is imperative that the ECM and TCM have an accurate reading here because they influence, among other things: shift points, speed, handling, etc.

The ECM triggers P0737 and related codes when it monitors one or more conditions outside a specific electrical range in the engine speed sensor or its circuit. Given the nature of the code and the sensor’s location, I would say most of the time, it would be an electrical issue. Specific mechanical problems can cause this code, but I would say they are somewhat rare.

P0737 TCM Engine Speed Output Circuit code is set when the ECM monitors a general malfunction or an open circuit in the engine speed output circuit(s).
How Severe Is This DTC?

I would say the severity here would be low. Obviously, it depends on the specific situation, but generally, this fault will only cause driving issues. That being said, prolonged use with this fault may cost you in the long run, so be sure to monitor it.

What Are Some of the Symptoms of the Code?

Symptoms of a P0737 trouble code may include:

Hard shifting
Decreased fuel consumption
No start
Low speed
Engine stalling/bypass
Inaccurate speedometer
Reduced throttle response

What Are Some Common Causes of the Code?

Causes

of this P0737 transmission code may include:

Faulty engine speed sensor (ESS)
Faulty ECM (engine control module)
Faulty TCM (transmission control module)
Wiring issue
Dirty pickup on the ESS
Connector problem

What Are the Troubleshooting Steps for P0737?

Be sure to check the technical service bulletins (TSB) for your vehicle. Access to a known fix can save you time and money during diagnosis.
Tools

Some of the things you might need when diagnosing or repairing engine speed output circuits and systems:

OBD code reader
Multimeter
Basic socket set
Ratchet and wrench sets
Basic screwdriver set
Battery terminal cleaner
Service manual

Safety Tips

Let the engine cool down
Chock the wheels
Wear PPE (personal protective equipment)

NOTE: ALWAYS check and record the integrity of your battery and charging system before proceeding with troubleshooting.
Basic Step No. 1

If your car’s engine cranks properly but does not start, it may indicate a problem with the ESS (engine speed sensor) itself. Test the sensor using the manufacturer’s desired electrical values. Repair or replace accordingly. Typically, these sensors read crankshaft speed, so it would most likely be mounted somewhere on the engine block.
Basic Step #2

Check your fluids. Be sure to check the automatic transmission fluid. Make sure it is clean and full. Top up if necessary. Low fluid level can cause automatic transmissions to behave erratically, so go ahead! Black or extremely dark transmission fluid will need to be replaced to ensure proper transmission function. Not only can low and/or dirty transmission fluid trigger this code, but it can further damage internal transmission components. This is one of the most expensive repairs in the business, so make sure the correct clean fluid is present.

NOTE: Always use the transmission fluid recommended by the manufacturer specific to your make and model. A mistake here could potentially cost thousands. Do your research!
Basic Step #3

Check the wiring. Given the location of the ESS, the wires are exposed to the elements and road debris. Inspect for any damage to the harness. Chafing can occur if the harness is routed near the engine and other sharp components. Repair any damaged wiring.

NOTE: Refer to your service manual to ensure you correctly identify the desired wiring harness.
Basic Step #4

Clean the sensor. It may be quite simple to remove the ESS. In this case, remove the sensor from the engine block. Inspect the sensor’s pickup; after all, they are magnetic and are extremely likely to pick up debris/shavings that could potentially alter electrical readings. Reinstall the sensor once it is cleaned and free of debris.
Basic Step #5

Inspect the TCM (Transmission Control Module). I have seen them mounted directly on the transmission many times. This means this electrical module is exposed to harsh conditions. That said, take a look for any signs of corrosion, damage, and/or any kind of fault.

Low TCM Engine Speed Output Circuit

What Does It Mean?

The TCM uses various sensors and switches along with the ECM to monitor, control, and regulate transmission operation. Specifically, the TCM uses an Engine Speed Sensor (ESS) to determine shift points among other functions. Just as its name implies, the ESS monitors engine speed. Other names for the ESS may be CKP (Crankshaft Position Sensor) or OSS (Output Speed Sensor).

Most of the time, it measures crankshaft speed using a Hall effect type sensor. The sensor uses notches in the flywheel that pass through the sensor to monitor crankshaft position. It is imperative that the ECM and TCM have an accurate reading here as they influence, among other things: shift points, speed, drivability, etc.

The ECM triggers P0738 and related codes when it monitors one or more conditions outside a specific electrical range in the engine speed sensor or its circuit. Given the nature of the code and the sensor’s location, I would say most of the time, it would be an electrical issue. Specific mechanical problems can cause this code but I would say they are somewhat rare.

P0738 TCM Engine Speed Output Circuit Low code is set when the ECM recognizes a low electrical value in the engine speed output circuit(s).
How Severe Is This DTC?

I would say the severity here would be low. Obviously, it depends on the specific situation but generally, this fault will only cause driving issues. That being said, prolonged use with this fault may cost you in the long run, so be sure to monitor it.

What Are Some of the Symptoms of the Code?

Symptoms of a P0738 fault code may include:

Harsh shifting
Decreased fuel consumption
No start
Low speed
Engine stalling/surging
Inaccurate speedometer
Reduced throttle response

What Are Some of the Common Causes of the Code?

Causes

of this P0738 transmission code may include:

Faulty engine speed sensor (ESS)
Faulty ECM (Engine Control Module)
Faulty TCM (Transmission Control Module)
Wiring issue
Dirty pickup on the ESS
Connector problem

What Are the P0738 Troubleshooting Steps?

Be sure to check the Technical Service Bulletins (TSBs) for your vehicle. Accessing a known fix can save you time and money during diagnosis.
Tools

Some of the things you might need when diagnosing or repairing engine speed output circuits and systems:

OBD code reader
Multimeter
Basic socket set
Ratchet and wrench sets
Basic screwdriver set
Battery terminal cleaner
Service manual

Safety Tips

Let the engine cool down
Chock the wheels
Wear PPE (Personal Protective Equipment)

NOTE: ALWAYS check and record the integrity of your battery and charging system before proceeding with troubleshooting.
Basic Step #1

If your car’s engine cranks properly but does not start, it may indicate a problem with the ESS (Engine Speed Sensor) itself. Test the sensor using the manufacturer’s desired electrical values. Repair or replace accordingly. Typically, these sensors read crankshaft speed so it would most likely be mounted somewhere on the engine block.
Basic Step #2

Check your fluids. Be sure to check the automatic transmission fluid. Ensure it is clean and full. Top up if necessary. Low fluid level can cause automatic transmissions to do funny things, so go ahead! Black or extremely dark transmission fluid will need to be replaced to ensure proper transmission function. Not only can low and/or dirty transmission fluid trigger this code, but it can further damage internal transmission components. Which is one of the most expensive repairs in the business, so make sure the correct clean fluid is present.

NOTE: Always use the transmission fluid recommended by the manufacturer specific to your make and model. A mistake here could potentially cost thousands. Do your research!
Basic Step #3

NOTE: Refer to your service manual to ensure you correctly identify the desired wiring harness.
Basic Step #4

Clean the sensor. It may be straightforward enough to remove the ESS. In that case, remove the sensor from the engine block. Inspect the sensor pickup; after all, they are magnetic and are extremely likely to pick up debris/shavings that could potentially alter electrical readings. Reinstall the sensor once cleaned and free of debris.
Basic Step #5

GMC P1442 Code: EVAP System Flow During Non-Purge Explained

Understanding the GMC P1442 Trouble Code

The P1442 diagnostic trouble code is a manufacturer-specific code primarily affecting GMC vehicles, including popular models like the Sierra, Yukon, and Acadia. This code indicates a fault in the Evaporative Emission Control (EVAP) system, specifically “EVAP System Flow During Non-Purge.” When your GMC’s Powertrain Control Module (PCM) detects vapor flow through the EVAP system when the purge cycle is not active, it triggers this code and illuminates the check engine light.

What Does P1442 Mean for Your GMC?

The P1442 code signifies that your vehicle’s computer has detected an unexpected flow of fuel vapors through the EVAP system during periods when the system should be sealed. Modern EVAP systems operate in precise cycles: purge and non-purge. During non-purge conditions, the system should remain completely closed to prevent fuel vapors from escaping into the atmosphere. The PCM monitors this through various sensors, primarily the fuel tank pressure sensor and purge flow sensors.

The EVAP System’s Role in Your Vehicle

The Evaporative Emission Control system is crucial for both environmental protection and vehicle performance. Its primary functions include:

Capturing fuel vapors from the fuel tank before they can escape into the atmosphere
Storing these vapors in the charcoal canister until the engine can safely burn them
Preventing hydrocarbon emissions that contribute to air pollution
Maintaining proper fuel system pressure for optimal engine performance
Ensuring compliance with stringent emission regulations

Common Causes of P1442 in GMC Vehicles

Diagnosing a P1442 code requires understanding the various components that could be malfunctioning. The EVAP system is complex, with multiple potential failure points that can trigger this specific code.

Vent Valve Circuit Malfunctions

The EVAP canister vent valve is one of the most common culprits for P1442 codes. This electrically-operated valve controls the flow of air into and out of the charcoal canister. Common vent valve issues include:

Stuck open vent valve solenoid preventing proper system sealing
Electrical faults in the vent valve control circuit
Corroded wiring connectors or damaged harnesses
Mechanical binding in the valve mechanism due to contamination
Failed vent valve actuator motor in more modern systems

Vacuum Leaks and System Integrity Issues

Unwanted vacuum leaks can create the flow conditions that trigger P1442. These leaks can occur in various locations throughout the EVAP system:

Cracked or deteriorated EVAP hoses and lines
Loose or missing gas cap (though this often triggers different codes)
Damaged charcoal canister housing
Faulty purge valve stuck in partially open position
Corroded fuel tank filler neck or vent lines

Control Module and Sensor Failures

Sometimes the problem isn’t with the mechanical components but with the electronic controls monitoring them:

Faulty fuel tank pressure sensor providing incorrect readings
PCM software issues or calibration errors
Wiring harness damage between sensors and the PCM
Ground connection problems affecting sensor accuracy
Communication bus errors in modern CAN-based systems

Step-by-Step Diagnostic Procedure for P1442

Proper diagnosis of P1442 requires a systematic approach using appropriate tools and following logical testing sequences. Always begin with visual inspection before moving to electronic testing.

Initial Inspection and Preliminary Checks

Start with these basic checks that often reveal obvious problems:

Verify the gas cap is properly tightened and in good condition
Conduct thorough visual inspection of all EVAP system components
Check for damaged, cracked, or disconnected hoses
Inspect electrical connectors for corrosion or damage
Look for signs of physical damage to the charcoal canister
Check for stored freeze frame data to understand driving conditions when code set

Advanced Diagnostic Testing Methods

When visual inspection doesn’t reveal the issue, proceed with these technical diagnostic procedures:

Perform smoke machine test to identify vacuum leaks in the EVAP system
Use bidirectional scanner controls to command vent valve operation
Test vent valve electrical circuit for proper voltage and ground signals
Measure vent valve resistance and compare to manufacturer specifications
Monitor fuel tank pressure sensor data during key-on engine-off tests
Check for proper purge valve operation and sealing capability

Repair Procedures and Technical Solutions

Once you’ve identified the root cause of the P1442 code, proper repair procedures are essential for permanent resolution.

Vent Valve Replacement Procedure

Replacing a faulty EVAP canister vent valve typically follows this sequence:

Disconnect negative battery cable for safety
Locate vent valve (usually near fuel tank or charcoal canister)
Disconnect electrical connector and vent hoses
Remove mounting bolts or retaining clips
Install new vent valve using reverse procedure
Clear trouble codes and perform readiness monitor drive cycle
Verify repair with follow-up scan tool monitoring

Addressing Electrical and Vacuum Issues

For electrical and vacuum-related repairs, these steps ensure proper resolution:

Repair damaged wiring using proper solder and heat shrink techniques
Replace cracked or deteriorated vacuum hoses with OEM-quality parts
Test circuit integrity after repairs using digital multimeter
Perform system leak test after all repairs are complete
Verify all electrical connections are secure and protected from elements

Prevention and Maintenance Tips

Preventing P1442 and other EVAP system codes requires regular maintenance and awareness of potential issues.

Regular EVAP System Maintenance

Implement these maintenance practices to avoid EVAP system problems:

Always tighten gas cap until it clicks three times
Inspect EVAP system components during routine maintenance
Keep the area around the fuel filler neck clean and free of debris
Address check engine lights promptly to prevent additional damage
Use quality replacement parts when repairs are necessary

Professional vs. DIY Repair Considerations

Understanding when to seek professional help is crucial for proper repair:

Simple visual inspections and gas cap replacement are suitable for DIY
Electrical diagnosis and smoke testing typically require professional equipment
Warranty considerations may dictate professional service requirements
Emission system repairs may be covered under extended warranties
Complex diagnosis often requires factory scan tools and technical resources

Successfully diagnosing and repairing a P1442 code requires understanding the sophisticated interaction between mechanical and electronic components in your GMC’s EVAP system. While this code doesn’t typically cause immediate drivability issues, addressing it promptly ensures your vehicle remains emissions-compliant and prevents potential fuel system problems. Always consult your vehicle’s specific service information for detailed diagnostic procedures and torque specifications.

P0739 High TCM Engine Speed Output Circuit

What does it mean?

Most of the time, it measures crankshaft speed using a Hall effect type sensor. The sensor uses notches in the flywheel that pass by the sensor to monitor crankshaft position. It is imperative that the ECM and TCM have an accurate reading here because they influence, among other things: shift points, speed, drivability, etc.

The ECM sets P0739 and related codes when it monitors one or more conditions outside of a specific electrical range in the engine speed sensor or its circuit. Given the nature of the code and the sensor’s location, I would say most of the time, this would be an electrical issue. Specific mechanical problems can cause this code but I would say they are somewhat rare.

P0739 TCM Engine Speed Output Circuit High code is set when the ECM monitors a specific electrical value higher than desired in the engine speed output circuit(s).
How severe is this DTC?

I would say the severity here would be low. Obviously, it depends on the specific situation but generally, this fault will only cause driving issues. That being said, prolonged use with this fault can cost you in the long run, so be sure to monitor it.

What are some of the symptoms of the code?

Symptoms of a P0739 fault code may include:

Harsh shifting
Decreased fuel economy
No start
Low speed
Engine stalling/surging
Inaccurate speedometer
Less throttle response

What are some of the common causes of the code?

Causes

of this P0739 transmission code may include:

Faulty Engine Speed Sensor (ESS)
Faulty ECM (Engine Control Module)
Faulty TCM (Transmission Control Module)
Wiring problem
Dirty pickup on the ESS
Connector problem

What are the troubleshooting steps for P0739?

Be sure to check Technical Service Bulletins (TSBs) for your vehicle. Access to a known fix can save you time and money when diagnosing.
Tools

Some of the things you might need when diagnosing or repairing engine speed output circuits and systems:

OBD code reader
Multimeter
Basic socket set
Ratchet and wrench sets
Basic screwdriver set
Battery terminal cleaner
Service manual

Safety Tips

Let the engine cool down
Chock the wheels
Wear PPE (Personal Protective Equipment)

NOTE: ALWAYS check and record the integrity of your battery and charging system before proceeding with troubleshooting.
Basic Step No. 1

If your car’s engine cranks properly but does not start, this may indicate a problem with the ESS (Engine Speed Sensor) itself. Test the sensor using the manufacturer’s desired electrical values. Repair or replace accordingly. Typically, these sensors read crankshaft speed so it would most likely be mounted somewhere on the engine block.
Basic Step #2

Check your fluids. Be sure to check the automatic transmission fluid. Make sure it is clean and full. Top up if necessary. Low fluid level can cause automatic transmissions to do funny things, so go ahead! Black or extremely dark transmission fluid will need to be replaced to ensure proper transmission function. Not only can low and/or dirty transmission fluid trigger this code, but it can further damage internal transmission components. This is one of the most expensive repairs in the business, so make sure the correct clean fluid is present.

NOTE: Always use the transmission fluid recommended by the manufacturer specific to your make and model. A mistake here could potentially cost thousands. Do your research!
Basic Step #3

NOTE: Refer to your service manual to ensure you correctly identify the desired wiring harness.
Basic Step #4

Clean the sensor. It may be simple enough to remove the ESS. In this case, remove the sensor from the engine block. Inspect the sensor tip; after all, they are magnetic and are extremely likely to pick up debris/shaving that can potentially alter electrical readings. Reinstall the sensor once it is cleaned and free of debris.
Basic Step #5