P0977: Shift Solenoid B Control Circuit High

Definition

The OBD2 code P0977 indicates that there is a high voltage signal detected in the control circuit for Shift Solenoid B, which may suggest a malfunction in the solenoid or its circuit

Common causes

Faulty shift solenoid B
Wiring issues (short circuit or open circuit)
Poor electrical connections
Faulty transmission control module (TCM)
Low transmission fluid level
Contaminated transmission fluid
Internal transmission failure

Common misdiagnoses

Faulty shift solenoid
Transmission fluid issues (low or contaminated fluid)
Wiring or connector problems
Transmission control module (TCM) failure
Internal transmission damage
Faulty engine control module (ECM)
Incorrectly diagnosed transmission issues
Sensor malfunctions (e.g., speed sensors)

Troubleshooting steps

1. Check for Additional Codes

Use an OBD-II scanner to check for any other related trouble codes. This can provide more context and help identify if there are multiple issues
2. Inspect Wiring and Connectors
3. Visually inspect the wiring and connectors associated with the shift solenoid B. Look for signs of damage, corrosion, or loose connections
4. Pay special attention to the wiring harness for any fraying or breaks
5. Test the Shift Solenoid
6. Disconnect the shift solenoid connector and use a multimeter to test the solenoid's resistance. Compare the reading to the manufacturer's specifications
7. If the solenoid is out of spec, it may need to be replaced
8. Check the Power and Ground
9. With the ignition on (engine off), use a multimeter to check for voltage at the solenoid connector. You should see battery voltage
10. Also, check for a good ground connection. If there is no voltage or ground, trace the circuit back to the transmission control module (TCM) or power source
11. Inspect the Transmission Control Module (TCM)
12. If the solenoid and wiring are in good condition, the issue may lie with the TCM. Check for any signs of damage or corrosion
13. If possible, perform a TCM reset or reprogramming, as sometimes software issues can cause erroneous codes
14. Check for Fluid Issues
15. Low or contaminated transmission fluid can affect solenoid operation. Check the fluid level and condition, and replace it if necessary
16. Perform a Visual Inspection of the Transmission
17. Look for any signs of leaks or damage to the transmission that could affect solenoid operation
18. Consult Technical Service Bulletins (TSBs)
19. Check for any TSBs related to your vehicle's make and model that might address known issues with the shift solenoid or transmission control system
20. Clear the Codes and Test Drive
21. After performing repairs or inspections, clear the codes and take the vehicle for a test drive to see if the code returns
22. Seek Professional Help
23. If the issue persists after following these steps, it may be best to consult a professional mechanic or technician who has experience with transmission issues. By following these steps, you should be able to diagnose and potentially resolve the issue related to the P0977 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 B. Look for signs of damage, corrosion, or loose connections

4. Pay special attention to the wiring harness for any fraying or breaks

5. Test the Shift Solenoid

6. Disconnect the shift solenoid connector and use a multimeter to test the solenoid's resistance. Compare the reading to the manufacturer's specifications

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

8. Check the Power and Ground

9. With the ignition on (engine off), use a multimeter to check for voltage at the solenoid connector. You should see battery voltage

10. Also, check for a good ground connection. If there is no voltage or ground, trace the circuit back to the transmission control module (TCM) or power source

11. Inspect the Transmission Control Module (TCM)

12. If the solenoid and wiring are in good condition, the issue may lie with the TCM. Check for any signs of damage or corrosion

13. If possible, perform a TCM reset or reprogramming, as sometimes software issues can cause erroneous codes

14. Check for Fluid Issues

15. Low or contaminated transmission fluid can affect solenoid operation. Check the fluid level and condition, and replace it if necessary

16. Perform a Visual Inspection of the Transmission

17. Look for any signs of leaks or damage to the transmission that could affect solenoid operation

18. Consult Technical Service Bulletins (TSBs)

19. Check for any TSBs related to your vehicle's make and model that might address known issues with the shift solenoid or transmission control system

20. Clear the Codes and Test Drive

21. After performing repairs or inspections, clear the codes and take the vehicle for a test drive to see if the code returns

22. Seek Professional Help

23. If the issue persists after following these steps, it may be best to consult a professional mechanic or technician who has experience with transmission issues. By following these steps, you should be able to diagnose and potentially resolve the issue related to the P0977 code