P0978 - Shift Solenoid "C" Control Circuit Range/Performance

P0978 – OBD-II Trouble Code Technical Description

Shift Solenoid "C" Control Circuit Range/Performance

What does the fault code mean P0978?

Trouble code P0978 refers to the electronic torque converter pressure solenoid valve control system. More specifically, this code means “Pressure Control Solenoid “C” Control Circuit Low.”

This code indicates a low signal in the electrical circuit that controls solenoid C. Solenoids are used to regulate pressure in the transmission, and if they do not work properly, they can cause problems with shifting and other transmission performance.

Possible reasons

Possible causes of a P0978 code may include:

1. Solenoid C fault: Problems with the solenoid valve itself, such as a short circuit or open circuit.
2. Damaged wires or connectors: Problems with wires, connections or connectors in an electrical circuit, including corrosion.
3. Problems with the electrical transmission system: For example, problems with the transmission controller or other control system components.
4. Problems with sensors or position sensors: Problems with sensors responsible for monitoring pressure or position inside the transmission torque converter.

To accurately identify and correct the problem, it is recommended to carry out diagnostics using the appropriate equipment and service manual for your specific vehicle make and model.

What are the symptoms of a fault code? P0978?

Symptoms for trouble code P0978 (Pressure Control Solenoid “C” Control Circuit Low) can vary depending on the specific problem with the C solenoid control system. Here are some possible symptoms:

1. Gearshift problems: One of the most common symptoms is incorrect or delayed gear shifting. This may include shifting jerks, shift delays, or other transmission anomalies.
2. Unusual sounds: Problems with the C solenoid can cause unusual noises in the transmission, such as knocking, squeaking, or humming.
3. Errors in engine operation: Low transmission pressure caused by solenoid problems can cause the engine to run rough, which may include extra load or changes in idle speed.
4. Check Engine Light: An illuminated Check Engine light on your dashboard is a typical sign of a problem with the electronic engine and transmission control system. Code P0978 will be stored in the control module memory.
5. Degraded performance and fuel consumption: Transmission problems can affect the overall performance of the vehicle and lead to increased fuel consumption.

If you experience these symptoms, it is recommended that you contact a qualified auto mechanic to diagnose and repair the problem.

How to diagnose a fault code P0978?

To diagnose trouble code P0978 (Pressure Control Solenoid “C” Control Circuit Low), the following approach is recommended:

1. Scanning error codes: Use a diagnostic scan tool to read error codes in the electronic engine and transmission control system. The P0978 code will indicate a specific problem with solenoid C control.
2. Visual check of wires and connectors: Carefully inspect the wires and connectors associated with solenoid C. Check for damage, corrosion, or breaks. Disconnect and check the connectors for signs of poor contact.
3. Resistance measurement: Using a multimeter, measure the resistance in the solenoid C control circuit. The normal resistance may be listed in the service manual for your specific vehicle make and model.
4. Checking Solenoid C: Check solenoid C itself for corrosion, breaks or other mechanical damage. If necessary, replace the solenoid.
5. Checking transmission pressure: Use a diagnostic scan tool to monitor transmission pressure while the vehicle is running. Low pressure may be due to problems with solenoid C control.
6. Checking sensors and sensors: Check the operation of transmission-related sensors such as position and pressure sensors.
7. Checking the electrical transmission system: Check transmission control system components, such as the transmission controller, for damage or malfunction.
8. Professional diagnostics: If you cannot identify and fix the problem yourself, it is recommended that you contact a professional auto mechanic or service center. They may use more advanced diagnostic methods, such as testing using special equipment.

It is important to note that diagnosing and repairing transmissions requires certain skills and experience, so if you do not have the relevant experience, it is better to turn to professionals.

Diagnostic errors

When diagnosing the P0978 trouble code and looking for the correct cause of the problem, some common errors may include:

1. Skip visual inspection of wires and connectors: Some technicians may neglect to visually inspect wires and connectors, which can result in problems such as breaks, corrosion, or loose connections being missed.
2. Insufficient checking of solenoid C: Problems with the C solenoid itself, such as corrosion or mechanical damage, may be missed during diagnosis. Careful inspection of solenoid C is important for correct diagnosis.
3. Ignoring other error codes: Other transmission or electrical system related error codes may also affect solenoid C operation. Missing them may result in a misdiagnosis.
4. Unaccounted environmental factors: Electromagnetic interference, humidity, or other environmental factors may affect electrical components. They should also be taken into account when diagnosing.
5. Insufficient transmission pressure check: Measuring transmission pressure can be a key diagnostic step. Insufficient pressure testing may result in problems related to C solenoid control being missed.
6. Incorrect component replacement: Replacing the C solenoid or other components without careful diagnosis may not be effective. All necessary tests must be carried out to ensure that a particular component is faulty.
7. Unaccounted for mechanical problems: Transmission problems such as wear or mechanical damage can cause solenoid C problems and should also be considered during diagnosis.

For successful diagnosis, a systematic approach and a thorough check of all possible factors affecting the operation of solenoid C and the transmission as a whole are recommended.

How serious is the fault code? P0978?

Trouble code P0978 indicates a problem with solenoid C control in the transmission, which can affect shifting. The severity of this code depends on several factors:

1. Impact on transmission: Problems with the C solenoid can cause rough shifting, jerking, hesitation, or other transmission abnormalities. This can significantly impair driving comfort and road safety.
2. Possible damage: If C solenoid problems are not corrected promptly, it can cause additional damage to the transmission or other vehicle components.
3. Fuel consumption: A transmission that is not operating properly can also affect your fuel economy as it may be less efficient.
4. Check Engine Light: In addition to problems with the transmission, the inclusion of the Check Engine light can also be a reason for dissatisfaction with the technical condition of the car.
5. Possibility of movement: Depending on how severe the problem with solenoid C is, it may affect the vehicle's drivability.

Overall, the P0978 code should be taken seriously and it is recommended that you begin diagnosing and repairing the problem as soon as possible. If you notice symptoms associated with this code or are concerned about the Check Engine Light on your dashboard, it is recommended that you take it to a qualified mechanic for more detailed diagnosis and repair.

What repair will help eliminate the code? P0978?

Troubleshooting trouble code P0978 (Pressure Control Solenoid “C” Control Circuit Low) may involve several steps depending on the specific cause of the problem. Here are some possible remedies for this code:

1. Solenoid C replacement: If solenoid C is truly faulty, then replacement may be necessary. Replacing the solenoid requires specific procedures and may vary depending on the transmission design.
2. Repair or replacement of wiring and connectors: Check the wiring and connectors associated with solenoid C. If damage, corrosion, or broken wires are found, they can be repaired or replaced.
3. Checking and replacing the transmission controller: If the problem is with the transmission controller, it may need to be replaced or programmed. Transmission controllers can be rebuilt, but sometimes require replacement.
4. Checking transmission pressure: Measuring the transmission pressure can help determine if there are pressure problems affecting solenoid C operation. Pressure adjustments or pressure parts replacement may be necessary.
5. Checking sensors and sensors: Check transmission-related sensors such as pressure or position sensors. Replacing faulty sensors may resolve problems.
6. Diagnosis of mechanical problems: If transmission problems are related to mechanical components, such as clutches or friction plates, mechanical intervention may be required.

It is recommended to conduct a detailed diagnosis using specialized equipment and tools. If you are not experienced in transmission repair, it is recommended that you take it to a professional mechanic or service center to accurately diagnose and repair the problem.

What is P0978 Engine Code [Quick Guide]

P0978 – Brand-specific information

Trouble codes such as P0978 may have a general meaning, but the exact meaning may vary depending on the vehicle manufacturer. Here are some examples of decryptions for various brands:

1. Ford, Lincoln, Mercury:
   • P0978: Shift Solenoid “C” Control Circuit Low
2. Chevrolet, GMC, Cadillac, Buick:
   • P0978: Shift Solenoid “C” Control Circuit Low
3. Toyota, Lexus:
   • P0978: Shift Solenoid “C” Control Circuit Low
4. Honda, Acura:
   • P0978: Shift Solenoid “C” Control Circuit Low
5. Nissan, Infiniti:
   • P0978: Shift Solenoid “C” Control Circuit Low
6. Volkswagen, Audi, Porsche:
   • P0978: Shift Solenoid “C” Control Circuit Low
7. BMW, Mini:
   • P0978: Shift Solenoid “C” Control Circuit Low
8. Mercedes Benz:
   • P0978: Shift Solenoid “C” Control Circuit Low
9. Subaru:
   • P0978: Shift Solenoid “C” Control Circuit Low
10. Hyundai, Kia:
    • P0978: Shift Solenoid “C” Control Circuit Low

Please note that these are general descriptions and there may be differences depending on the specific model and year of the vehicle. For more accurate information, it is recommended that you refer to the manufacturer's official service manuals or consult your vehicle brand dealer.