P078C Shift Timing Solenoid B Low

What does it mean?

This is a generic diagnostic trouble code (DTC) and generally applies to OBD-II equipped vehicles with an automatic transmission. Vehicle makes may include, but are not limited to, Chevrolet/Chevy, Volvo, GMC, Saab, Subaru, VW, BMW, Toyota, Ford, Dodge, etc.

The shift timing solenoid is one of many components that allow an automatic transmission to shift smoothly according to your driving needs. The TCM (Transmission Control Module) monitors and controls the functionality of the solenoids.

The main purpose of the solenoids is to control the internal hydraulic flow (ATF: Automatic Transmission Fluid) to help move the transmission. These solenoids are essentially electromechanical “pistons.” Most of the time, there are multiple shift timing solenoids in the system, so you can refer to the letter included in the code to identify the specific solenoid you are working with based on your make and model.

The ECM (Engine Control Module) illuminates the MIL (Malfunction Indicator Lamp) with P078C and related codes (P078A, P078B, P078D, and P078E) when it detects one or more issues in the shift timing solenoid or its circuit. The circuit includes the TCM, which, depending on the model, might be located in a volatile area. There are many possible causes here, so it could be mechanical and/or electrical depending on the code and whether others are active. Automatic transmissions are complexly designed systems, and in my opinion, the layperson or average DIYer should leave this to the pros, especially when it comes to internal transmission work.

The P078C Shift Timing Solenoid B code is set when the ECM (Engine Control Module) and/or TCM (Transmission Control Module) detects a specific low electrical value in the Shift Timing Solenoid B circuit.
How severe is this DTC?

I would say this code is moderately severe. If this issue is not fixed for too long, you risk seriously damaging the transmission, not to mention your wallet.
What are some of the symptoms of the code?

Symptoms of a P078C trouble code may include:

Stuck in gear
Irregular shifting
Transmission slipping
Hard or harsh shifting
Inefficient timing
Poor driving
Poor acceleration
Poor overall performance

What are some of the common causes of the code?

Causes

of this P078C transmission code may include:

Damaged or faulty shift timing solenoid
Dirty automatic transmission fluid (ATF)
Low ATF
Obstruction in ATF passages
Broken or damaged wiring harness
TCM issue
ECM issue
Pin/connector problem (corrosion, melting, broken locking tab, etc.)

What are the troubleshooting steps for P078C?

The first thing I would do here is check the ATF (Automatic Transmission Fluid). If the fluid is dirty, smells burnt, is overfilled, and/or has an abnormal color, it may be time to change your fluid. If you have owned your vehicle for 30,000 to 60,000 miles (50,000 to 100,000 kilometers) and don’t remember changing your fluid or have records of it, not only could this be your problem, but it could be avoided simply by following your maintenance schedule. Just something to think about! Old fluid is dirty fluid, dirty fluid can cause blockages, and blockages can cause this code, so change your fluid!

NOTE: Follow the manufacturer’s recommended steps when checking the ATF. This simple step can vary significantly between makes and models.
Basic Step #2

Is the fluid good, the code still active, and symptoms present? Depending on your specific model, the shift solenoid may be accessible from the outside. If so, inspect the solenoid and its harness/connectors for any signs of damage. Repair/replace any issues as needed. This is also a good time to check for any leaks!

TECH TIP: If your shift solenoid is internal, I do not recommend trying to access it; bypass it for now. Exhaust other avenues; diagnosing and repairing internal transmissions should be left to a certified technician.

NOTE: The TCM and harness involved in this circuit may be exposed to harsh road conditions, so make sure everything is intact and as it should be.
Basic Step #3

Test the shift timing solenoid. You may be able to test the solenoid itself in several ways. One test might include a resistance test where you use a multimeter to measure the resistance between the solenoid pins to check its electrical integrity to some extent. Another might involve manually applying voltage to the solenoid to check its mechanical operation. Either should be specified in your manufacturer’s service manual/technical documentation.
Basic Step #4

Test the circuit from the TCM. You may be able to check the sensor’s functionality and its circuit by performing the same tests as above but from the TCM and/or ECM pins. This is a good trick to check not only the solenoid’s integrity but also the electrical integrity of the circuit.

P078D High Shift B Timing Solenoid

What Does It Mean?

The ECM (Engine Control Module) illuminates the MIL (Malfunction Indicator Lamp) with P078D and related codes (P078A, P078B, P078C, and P078E) when it detects one or more issues in the shift timing solenoid or its circuit. The circuit includes the TCM, which, depending on the model, might be located in a volatile area. There are many possible causes here, so it could be mechanical and/or electrical depending on the code and if others are active. Automatic transmissions are complexly designed systems, and in my opinion, the layperson or average DIYer should leave this to the pros, especially when it comes to internal transmission work.

The P078D Shift Timing Solenoid B High code is set when the ECM (Engine Control Module) and/or TCM (Transmission Control Module) detects a specific high electrical value in the Shift Timing Solenoid B circuit.
How Severe Is This DTC?

I would say this code is moderately severe. If this issue is not fixed for too long, you risk seriously damaging the transmission, not to mention your wallet.
What Are Some of the Symptoms of the Code?

Symptoms of a P078D trouble code may include:

Stuck in gear
Irregular shifting
Transmission slipping
Hard or harsh shifting
Inefficient timing
Poor driving
Poor acceleration
Poor overall performance

What Are Some of the Common Causes of the Code?

Causes

of this P078D transmission code may include:

What Are the Troubleshooting Steps for P078D?

Before starting the troubleshooting process for any malfunction, you should look up the Technical Service Bulletins (TSBs) for the specific vehicle by year, model, and transmission. This step can save you time and money during diagnosis and repair!
Basic Step #1

The first thing I would do here is check the ATF (Automatic Transmission Fluid). If the fluid is dirty, smells burnt, is overfilled, and/or has an abnormal color, it may be time to change your fluid. If you have owned your vehicle for 30,000 to 60,000 miles (50,000 to 100,000 kilometers) and don’t remember changing your fluid or have records of it, not only could this be your problem, but it could have been avoided simply by following your maintenance schedule. Just something to think about! Old fluid is dirty fluid, dirty fluid can cause blockages, and blockages can cause this code, so change your fluid!

NOTE: Follow the manufacturer’s recommended steps when checking the ATF. This simple step can vary significantly between makes and models.
Basic Step #2

Is the fluid good, the code still active, and symptoms present? Depending on your specific model, the shift solenoid may be accessible from the outside. If so, inspect the solenoid and its harness/connectors for any signs of damage. Repair/replace any issues as necessary. This is also a good time to check for any leaks!

TECH TIP: If your shift solenoid is internal, I do not recommend trying to access it; skip it for now. Exhaust other avenues; diagnosing and repairing internal transmissions should be left to a certified technician.

NOTE: The TCM and harness involved in this circuit may be exposed to harsh road conditions, so make sure everything is intact and as it should be.
Basic Step #3

Test the shift timing solenoid. You may be able to test the solenoid itself in several ways. One test might include a resistance test where you use a multimeter to measure the resistance between the pins in the solenoid to check its electrical integrity to some extent. Another might involve manually applying voltage to the solenoid to check its mechanical operation. Either should be specified in your manufacturer’s service manual/technical documentation.
Basic Step #4

Test the circuit from the TCM. You may be able to check the functionality of the sensor and its circuit by performing the same tests as above but from the TCM and/or ECM pins. This is a good trick to check not only the solenoid’s integrity but also the electrical integrity of the circuit.

P078E Intermittent Shift Timing Solenoid B

What does it mean?

The ECM (Engine Control Module) illuminates the MIL (Malfunction Indicator Lamp) with P078E and related codes (P078A, P078B, P078C, and P078D) when it detects one or more issues in the shift timing solenoid or its circuit. The circuit includes the TCM, which, depending on the model, might be located in a volatile area. There are many possible causes here, so it could be mechanical and/or electrical depending on the code and whether others are active. Automatic transmissions are complexly designed systems, and in my opinion, the layperson or average DIYer should leave this to the pros, especially when it comes to internal transmission work.

The P078E Intermittent Shift Timing Solenoid B code is set when the ECM (Engine Control Module) and/or TCM (Transmission Control Module) detects a fault that is not consistent in the shift solenoid B circuit.
How severe is this DTC?

Symptoms of a P078E trouble code may include:

Stuck in gear
Irregular shifting
Transmission slipping
Hard or harsh shifting
Inefficient timing
Poor driving
Poor acceleration
Poor overall performance

What are some of the common causes of the code?

Causes

of this P078E transmission code may include:

What are the troubleshooting steps for P078E?

The first thing I would do here is check the ATF (Automatic Transmission Fluid). If the fluid is dirty, smells burnt, is overfilled, and/or has an abnormal color, it may be time to change your fluid. If you have owned your vehicle for 30,000 to 60,000 miles (50,000 to 100,000 kilometers) and don’t remember changing your fluid or have records of it, not only could this be your problem, but it can be avoided simply by following your maintenance schedule. Just something to think about! Old fluid is dirty fluid, dirty fluid can cause blockages, and blockages can cause this code, so change your fluid!

NOTE: Follow the manufacturer-recommended steps when checking the ATF. This simple step can vary significantly between makes and models.
Basic Step #2

TECH TIP: If your shift solenoid is internal, I do not recommend trying to access it; skip it for now. Exhaust other avenues; diagnosing and repairing internal transmissions should be left to a certified technician.

NOTE: The TCM and harness involved in this circuit may be exposed to harsh road conditions, so ensure everything is intact and as it should be.
Basic Step #3

P0790 Normal/Performance Switch Circuit Malfunction

What Does It Mean?

This is a generic diagnostic trouble code (DTC) for the powertrain and generally applies to OBD-II vehicles. This may include, but is not limited to, vehicles from GMC, Chevrolet, Ford, Buick, Dodge, etc. Although generic, the exact repair steps may vary depending on the year, make, model, and powertrain configuration.

The Transmission Control Module (TCM) monitors all sensors and switches involved in the transmission’s operation. Nowadays, automatic transmissions (also known as A/T) offer more comfort than ever before.

For example, cruise control is sometimes monitored and controlled by the TCM (among other possible modules). In this context, it applies to a normal/performance mode switch, which is activated by the operator to modify shift points and patterns to accommodate generally higher shift points and faster downshift points. The operation of this switch is essential for the performance function, among other systems that may be included. This will vary significantly by manufacturer, so be sure to know WHICH switch applies to your current issue and the specific make and model.

The ECM illuminates the MIL (Malfunction Indicator Lamp) with a P0790 code when it detects a malfunction in the normal/performance switch circuit. Most of the time, this switch is located on or near the gear shift lever. On a column shifter, it may be a button at the end of the lever. On console-style shifters, it may be on the dashboard or console. Since this location varies significantly from vehicle to vehicle, consult your service manual for the exact location.

How Severe Is This DTC?

I would rate this as low severity. That said, you may want to avoid aggressive or hard driving. This could put unnecessary stress on the transmission and its components, so be cautious here.
What Are Some of the Symptoms of the Code?

Symptoms of a P0790 trouble code may include:

    Inoperative mode switch
    Irregular and/or abnormal switch operation
    Inefficient shift pattern
    Weak battery
    No downshift when torque is needed

What Are Some Common Causes of the Code?

Causes

of this P0790 code may include:

    Faulty or damaged switch
    Corrosion causing high resistance (e.g., connectors, pins, grounds, etc.)
    Wiring issues (e.g., frayed, open, short to power, short to ground, etc.)
    Faulty gear shift lever
    TCM (Transmission Control Module) issue
    Fuse/box problem

What Are the Troubleshooting Steps for P0790?

Basic Step #1

Depending on the tools/references you have, your starting point may vary. That said, if your scanner has monitoring capabilities (DATA STREAM), you may be able to monitor the values and/or operation of your normal/performance switch. If so, toggle the switch on and off to see if your scanner recognizes your inputs. There may be a delay here, so allowing a few seconds is always a good idea when monitoring switches.

Not only that, but if you find the mode switch inoperative according to your scanner, you may be able to jump certain pins at the mode switch connector to rule out the circuit. If the circuit is ruled out this way and the switch is still inoperative, I would move on to testing the switch itself. Obviously, these are general guidelines, but with a moderately capable scan tool, troubleshooting CAN be painless if you know what you’re looking for. Refer to the service manual for specifications/procedures.

Basic Step #2

Test the switch itself, if possible. Most of the time, these switches are only meant to signal the appropriate module(s) (e.g., TCM, BCM (Body Control Module), ECM, etc.) so it can implement modified shift patterns. That said, the majority of those I’ve encountered are on/off style. This means a simple continuity test with an ohmmeter can determine the sensor’s functionality. Now, these sensors are sometimes integrated into the gear shift lever, so be sure to identify the connectors/pins you need to monitor with your multimeter.

NOTE: As with any transmission fault, always ensure fluid levels and quality are adequate and well-maintained.

Intermediate Shaft Speed Sensor, Circuit A

What does it mean?

This is a generic diagnostic trouble code (DTC) that generally applies to OBD-II vehicles with automatic transmissions. This may include, but is not limited to, vehicles from Mazda, Toyota, Chrysler, Ford, VW, Dodge, Jeep, Mercedes, Lexus, Chevrolet, etc.

Although generic, the exact repair steps can vary depending on the year, make, model, and powertrain configuration.

The intermediate shaft, also known as the layshaft, helps distribute rotational force from the input drive to the output shaft inside the transmission. The speed of the intermediate shaft depends on the gear you are in. In a manual transmission, the gear selector dictates this, so monitoring the intermediate shaft speed is not necessary.

On the other hand, in an automatic transmission, if you are in “D” mode, the gear ratio is determined by the TCM (Transmission Control Module) using several sensor inputs that all contribute to smooth and efficient shifting. One of the sensors included here is the intermediate shaft speed sensor. The TCM needs this specific input to help determine and adjust hydraulic pressures, shift points, and patterns. Experience in diagnosing other types of speed sensors (e.g., VSS (Vehicle Speed Sensor), ESS (Engine Speed Sensor), etc.) will help here, as most speed sensors are of similar design.

The ECM (Engine Control Module) together with the TCM (Transmission Control Module) can activate P0791 and related codes (P0792, P0793, P0794) when they detect a fault in the intermediate shaft speed sensor or its circuits. Sometimes, when the sensor fails, the TCM uses other speed sensors in the transmission and determines a “backup” hydraulic pressure to keep the automatic transmission functional, but this can vary significantly from one manufacturer to another.

The P0791 intermediate shaft speed sensor A circuit is defined by the ECM (Engine Control Module) and/or the TCM (Transmission Control Module) when it detects a general malfunction within the speed sensor A or its circuit. Refer to a vehicle-specific repair manual to determine which part is the “A” circuit for your particular application.

NOTE: Record all active codes in other systems if multiple warning lights are on (e.g., traction control, ABS, VSC, etc.).

How severe is this DTC?

I would say this fault is moderately severe. As mentioned earlier, your automatic transmission may still function properly. That said, it could also indicate one or more larger and more urgent issues. Diagnosing any transmission problem as soon as possible is the best strategy.
What are some of the symptoms of the code?

Symptoms of a P0791 error code may include:

Harsh shifting
Many dashboard warning lights illuminated
Poor driving performance
Irregular engine RPM

What are some common causes of the code?

Causes of this P0791 engine code may include:

Faulty or damaged intermediate shaft speed sensor
Electrical fault in the wiring between the speed sensor and the modules used
Internal ECM and/or TCM problem
Other related sensors/solenoids damaged or faulty (e.g., input shaft speed sensor, output shaft sensor, shift solenoid, etc.)
Dirty or low automatic transmission fluid (ATF)

What are the troubleshooting steps for P0791?

Basic Step #1

If you are looking up this code, I will assume you have already checked the transmission fluid level. If not, start with that. Ensure the fluid is clean and properly filled. Once the fluid is checked, you need to locate the intermediate shaft speed sensor. Often, these sensors are mounted directly on the transmission case.

You may even access the sensor under the hood; this may involve removing one or more components such as the air filter and box, various brackets, wires, etc., to reach it. Make sure the sensor and its corresponding connector are in good condition and fully connected.

TIP: Burnt-smelling ATF (automatic transmission fluid) is a sign that new fluid is needed, so don’t hesitate to perform a full transmission service with all new filters, gaskets, and fluids.

Basic Step #2

An easily accessible speed sensor should be removed and cleaned. This costs almost nothing, and if you find the sensor tip is excessively dirty once removed, you might be able to clean your problems away, literally. Use brake cleaner and a cloth to ensure a clean pickup on the sensor. Dirt and/or metal shavings here can interfere with sensor readings, so make sure yours is clean!

NOTE: Any signs of rubbing on the sensor may indicate improper spacing between the reluctor ring and the sensor. Most likely, the sensor has malfunctioned and is now hitting the ring. If a replacement sensor still doesn’t clear the issue, refer to the manufacturer’s procedures to adjust the gap between the sensor and the reluctor.

Basic Step #3

Test the sensor and its circuit. To test the sensor itself, you will need to use your multimeter and the manufacturer’s specific specifications to measure different electrical values between the sensor pins. A good tip is to perform these tests from the same wires but at the corresponding ECM or TCM connector pins. This will check the integrity of the involved harness as well as the sensor.

P0792 Intermediate Shaft A Speed Sensor Circuit Range

What Does It Mean?

Although generic, the exact repair steps may vary depending on the year, make, model, and powertrain configuration.

The intermediate shaft, otherwise known as the layshaft, helps distribute rotational force from the input drive to the output shaft inside the transmission. The speed of the intermediate shaft depends on which gear you are in. In a manual transmission, the gear selector dictates this, so monitoring the intermediate shaft speed is not necessary.

The ECM (Engine Control Module) in conjunction with the TCM (Transmission Control Module) can activate P0792 and related codes (P0791, P0793, P0794) when they detect a fault in the intermediate shaft speed sensor or its circuits. Sometimes, when the sensor fails, the TCM uses other speed sensors in the transmission and determines a “backup” hydraulic pressure to keep the automatic transmission functional, but this can vary significantly from one manufacturer to another.

The P0792 Intermediate Shaft Speed Sensor A Circuit Range/Performance code is set by the ECM (Engine Control Module) and/or the TCM (Transmission Control Module) when it detects an out-of-range condition in the A speed sensor or its circuit. Refer to a vehicle-specific repair manual to determine which part is the “A” circuit for your particular application.

NOTE: Record all active codes in other systems if multiple warning lights are on (e.g., traction control, ABS, VSC, etc.).

How Severe Is This DTC?

Symptoms of a P0792 trouble code may include:

Harsh shifting
Many dashboard warning lights on
Poor driving performance
Irregular engine RPM

What Are Some Common Causes of the Code?

Causes

of this P0792 engine code may include:

Faulty or damaged intermediate shaft speed sensor
Electrical fault in the wires between the speed sensor and the modules used
Internal ECM and/or TCM problem
Other related sensors/solenoids damaged or faulty (e.g., input shaft speed sensor, output shaft sensor, shift solenoid, etc.)
Dirty or low automatic transmission fluid (ATF)

What Are the Troubleshooting Steps for P0792?

Basic Step #1

If you are looking up this code, I will assume you have already checked the transmission fluid level. If not, start with that. Make sure the fluid is clean and properly filled. Once everything is fluid, you need to locate the intermediate shaft speed sensor. Often, these sensors are mounted directly on the transmission case.

You may even access the sensor under the hood; this may involve removing one or more components such as the air filter and box, various brackets, wires, etc., to reach it. Ensure the sensor and its corresponding connector are in good condition and fully connected.

TIP: Burnt-smelling ATF (automatic transmission fluid) is a sign that new fluid is needed, so don’t hesitate to perform a full transmission service with all new filters, seals, and fluids.
Basic Step #2

An easily accessible speed sensor should be removed and cleaned. This costs almost nothing, and if you find the sensor tip excessively dirty once removed, you might be able to clean your problems away, literally. Use brake cleaner and a cloth to ensure a clean pickup on the sensor. Dirt and/or debris here can affect sensor readings, so make sure yours is clean!

NOTE: Any sign of rubbing on the sensor may indicate inadequate spacing between the reluctor ring and the sensor. Most likely, the sensor has malfunctioned and is now hitting the ring. If a replacement sensor still doesn’t clear the ring, refer to the manufacturer’s procedures to adjust the gap between the sensor and the reluctor.
Basic Step #3

Test the sensor and its circuit. To test the sensor itself, you will need to use your multimeter and the manufacturer’s specific specifications to measure different electrical values between the sensor pins. A good trick is to perform these tests from the same wires but at the corresponding ECM or TCM connector pins. This will check the integrity of the involved harness as well as the sensor.

Intermediate Shaft Speed Sensor A No Signal Circuit

📌 What does code P0793 mean?

Code P0793 indicates that the intermediate shaft A speed sensor (or its circuit) is transmitting no signal to the transmission control module (TCM) or the engine control module (ECM).
This sensor is essential in automatic transmissions for measuring the rotational speed of an internal shaft and assisting with gear shift management.

⚠️ Severity of the problem

Severity: moderate to high

The vehicle may continue to run, but with irregular or degraded transmission behavior. This could mask a more serious issue, so prompt repair is strongly recommended.

🔍 Possible symptoms

Harsh or irregular gear shifts
Unstable engine RPM
Dashboard warning lights illuminated (Check Engine, ABS, traction control, etc.)
Abnormal driving behavior (unstable idle, jerking)

❗ Common causes

Faulty speed sensor (dirty, damaged, misaligned)
Damaged wiring or connectors (short circuit, corrosion, broken wires)
Problem with the TCM or ECM
Other related sensors failing (input, output, etc.)
Transmission fluid (ATF) dirty, burnt, or insufficient

🛠️ Diagnostic steps and solutions

✅ Step 1: Check ATF condition and level

Low level or dirty fluid → replace according to manufacturer recommendations
Check for leaks or burnt smells

✅ Step 2: Locate and inspect the sensor

The sensor is usually on the transmission housing
Remove obstructing components (air filter, brackets)
Visually inspect the sensor and its connector: dirt, corrosion, improper connection

✅ Step 3: Clean the sensor

If accessible, remove the sensor and clean it with brake cleaner
Check that there are no metal shavings or debris stuck

✅ Step 4: Test the sensor and its circuit

Use a multimeter to test continuity and resistance according to manufacturer specifications
Also perform tests at the TCM/ECM connector to check wiring harness integrity

💡 Additional tips

A misaligned sensor may rub against the reluctor ring → adjust spacing if necessary
When in doubt, replace the sensor: it’s inexpensive compared to a complete transmission failure
Record all other active codes (ABS, traction control, etc.) to get an overall view of the problem

Intermediate Shaft A Speed Sensor, Intermittent Circuit

What Does It Mean?

Although generic, the exact repair steps may vary depending on the year, make, model, and powertrain configuration.

On the other hand, in an automatic transmission, if you are in “D” mode, the gear ratio is determined by the TCM (Transmission Control Module) using several sensor inputs that all contribute to smooth and efficient gear shifting. One of the sensors included here is the intermediate shaft speed sensor. The TCM needs this specific input to help determine and adjust hydraulic pressures, shift points, and patterns. Experience in diagnosing other types of speed sensors (e.g., VSS (Vehicle Speed Sensor), ESS (Engine Speed Sensor), etc.) will help here, as most speed sensors are of similar design.

The ECM (Engine Control Module) in conjunction with the TCM (Transmission Control Module) can activate P0794 and related codes (P0791, P0792, P0793) when they detect a fault in the intermediate shaft speed sensor or its circuits. Sometimes, when the sensor fails, the TCM uses other speed sensors in the transmission and determines a “fallback” hydraulic pressure to keep the automatic transmission functional, but this can vary significantly from one manufacturer to another.

The code P0794 Intermediate Shaft Speed Sensor A Circuit Intermittent is set by the ECM (Engine Control Module) and/or the TCM (Transmission Control Module) when it detects an intermittent or erratic signal from speed sensor A or its circuit. Refer to a vehicle-specific repair manual to determine which part is the “A” circuit for your particular application.

NOTE: Record all active codes in other systems if multiple warning lights are on (e.g., traction control, ABS, VSC, etc.).

How Severe Is This DTC?

I would say this fault is moderately severe. As mentioned earlier, your automatic transmission may still function properly. That said, it could also be indicative of one or more larger and more urgent issues. Diagnosing any transmission problem as soon as possible is the best strategy.
What Are Some of the Symptoms of the Code?

Symptoms of a P0794 trouble code may include:

Harsh shifting
Many dashboard warning lights on
Poor driving performance
Irregular engine RPM

What Are Some Common Causes of the Code?

Causes

of this P0794 engine code may include:

What Are the P0794 Troubleshooting Steps?

Basic Step #1

If you are looking up this code, I will assume you have already checked the transmission fluid level. If not, start with that. Ensure the fluid is clean and properly filled. Once everything is fluid, you need to locate the intermediate shaft speed sensor. Often, these sensors are mounted directly on the transmission case.

You may even access the sensor under the hood; this may involve removing one or more components such as the air filter and box, various brackets, wires, etc., to access it. Make sure the sensor and its corresponding connector are in good condition and fully connected.

TIP: Burnt-smelling ATF (automatic transmission fluid) is a sign that new fluid is needed, so don’t hesitate to perform a full transmission service with all new filters, gaskets, and fluids.
Basic Step #2

An easily accessible speed sensor should be removed and cleaned. This costs almost nothing, and if you find the sensor tip is excessively dirty once removed, you might be able to clean your problems away, literally. Use brake cleaner and a cloth to ensure a clean pickup of the sensor. Dirt and/or metal shavings here can affect sensor readings, so make sure yours is clean!

NOTE: Any sign of rubbing on the sensor may indicate improper spacing between the reluctor ring and the sensor. Most likely, the sensor has malfunctioned and is now hitting the ring. If a replacement sensor still doesn’t clear the code, refer to the manufacturer’s procedures to adjust the gap between the sensor and the reluctor.
Basic Step #3

P0795 Pressure Control Solenoid C Malfunction

What does it mean?

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

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 P0795 is set, the Powertrain Control Module (PCM) has detected a problem with the transmission pressure control solenoid “C”. Most automatic transmissions contain at least three solenoids which are solenoids A, B, and C. Trouble codes related to solenoid “C” are codes P0795, P0796, P0797, P0798, and P0799. 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 gear ratio at the right time.
Code P0795 is set by the PCM when the pressure control solenoid “C” 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 P0795 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 P0795 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 P0795?

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.

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, the transmission pump, and the 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 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.
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 connector corrosion
Repairing or replacing wiring
Reprogramming 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 trouble code. This article is strictly informational, and the technical data and service bulletins specific to your vehicle should always take priority.

P0796 Pressure Control Solenoid C 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 fault code P0796 is set, the Powertrain Control Module (PCM) has detected a problem with the transmission pressure control solenoid “C”. Most automatic transmissions have at least three solenoids, which are solenoids A, B, and C. Fault codes related to solenoid “C” are codes P0795, P0796, P0797, P0798, and P0799. The code set is based on the specific malfunction that alerts the PCM and illuminates the Check Engine light.

Code P0796 is set by the PCM when the pressure control solenoid “C” 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 P0796 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 P0796 transmission code may include:

What are the troubleshooting steps for P0796?

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

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 specified 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.
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
Reprogramming 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 fix 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.