P0978: Shift Solenoid C Control Circuit Range/Performance

Definition

The OBD2 code P0978 indicates a problem with the shift solenoid C's control circuit, specifically related to its range or performance, suggesting that the solenoid is not functioning as expected within its operational parameters

Common causes

Faulty shift solenoid C
Wiring issues (shorts, opens, or corrosion)
Poor electrical connections
Transmission control module (TCM) malfunction
Low transmission fluid level or quality
Faulty transmission fluid temperature sensor
Internal transmission problems

Common misdiagnoses

Faulty transmission control module (TCM)
Wiring issues or shorts in the harness
Faulty shift solenoid A or B
Low transmission fluid level or quality
Transmission fluid pump issues
Internal transmission problems (e.g., clutches, bands)
Incorrectly installed or damaged transmission components
Engine control module (ECM) issues
Faulty sensors (e.g., throttle position sensor, vehicle speed sensor)
Software or calibration issues in the TCM

Troubleshooting steps

1. Check for Additional Codes

Use an OBD-II scanner to check for any other trouble codes that may be present. This can provide more context and help identify related issues
2. Inspect Wiring and Connectors
3. Visually inspect the wiring and connectors associated with the Shift Solenoid C. Look for signs of damage, corrosion, or loose connections
4. Ensure that the connectors are securely attached and that there are no broken wires
5. Test the Shift Solenoid
6. Use a multimeter to test the resistance of the Shift Solenoid C. Compare the readings to the specifications provided in the vehicle’s service manual
7. If the solenoid is out of specification, it may need to be replaced
8. Check Transmission Fluid
9. Inspect the transmission fluid level and condition. Low or dirty fluid can cause shifting issues and affect solenoid performance
10. If the fluid is low, top it off with the correct type of transmission fluid. If it is dirty or burnt, consider a transmission fluid change
11. Inspect the Transmission Control Module (TCM)
12. Check for any issues with the TCM, as it controls the operation of the shift solenoids. Ensure that the TCM is functioning properly and that there are no software issues
13. If necessary, reprogram or replace the TCM
14. Perform a Visual Inspection of the Transmission
15. Look for any signs of leaks or damage to the transmission itself. Mechanical issues within the transmission can also lead to solenoid performance problems
16. Check for Ground Issues
17. Ensure that the ground connections for the transmission and solenoids are secure and free of corrosion
18. Clear Codes and Test Drive
19. After performing the above checks and repairs, clear the trouble codes using the OBD-II scanner and take the vehicle for a test drive to see if the code returns
20. Consult a Professional
21. If the issue persists after performing these steps, it may be necessary to consult a professional mechanic or transmission specialist for further diagnosis and repair. By following these troubleshooting steps, you can identify and potentially resolve the issue associated with the P0978 code

Definition

Common causes

Common misdiagnoses

Troubleshooting steps

1. Check for Additional Codes

2. Inspect Wiring and Connectors

3. Visually inspect the wiring and connectors associated with the Shift Solenoid C. Look for signs of damage, corrosion, or loose connections

4. Ensure that the connectors are securely attached and that there are no broken wires

5. Test the Shift Solenoid

6. Use a multimeter to test the resistance of the Shift Solenoid C. Compare the readings to the specifications provided in the vehicle’s service manual

7. If the solenoid is out of specification, it may need to be replaced

8. Check Transmission Fluid

9. Inspect the transmission fluid level and condition. Low or dirty fluid can cause shifting issues and affect solenoid performance

10. If the fluid is low, top it off with the correct type of transmission fluid. If it is dirty or burnt, consider a transmission fluid change

11. Inspect the Transmission Control Module (TCM)

12. Check for any issues with the TCM, as it controls the operation of the shift solenoids. Ensure that the TCM is functioning properly and that there are no software issues

13. If necessary, reprogram or replace the TCM

14. Perform a Visual Inspection of the Transmission

15. Look for any signs of leaks or damage to the transmission itself. Mechanical issues within the transmission can also lead to solenoid performance problems

16. Check for Ground Issues

17. Ensure that the ground connections for the transmission and solenoids are secure and free of corrosion

18. Clear Codes and Test Drive

19. After performing the above checks and repairs, clear the trouble codes using the OBD-II scanner and take the vehicle for a test drive to see if the code returns

20. Consult a Professional

21. If the issue persists after performing these steps, it may be necessary to consult a professional mechanic or transmission specialist for further diagnosis and repair. By following these troubleshooting steps, you can identify and potentially resolve the issue associated with the P0978 code