P0885: TCM Power Relay Control Circuit /Open

Definition

The OBD2 code P0885 indicates a problem with the Transmission Control Module (TCM) power relay control circuit, specifically that the circuit is open or not functioning properly, which can prevent the TCM from receiving power

Common causes

Faulty TCM (Transmission Control Module)
Open or shorted wiring in the TCM power relay circuit
Bad TCM power relay
Corroded or damaged connectors
Blown fuse related to the TCM power circuit
Faulty ignition switch
Poor ground connection for the TCM or relay

Common misdiagnoses

Transmission Control Module (TCM) failure
Faulty wiring or connectors
Battery or charging system issues
Faulty transmission solenoids
Engine Control Module (ECM) issues
Incorrectly diagnosed transmission problems
Faulty power relay
Grounding issues
Software or programming errors
Other electrical system faults

Troubleshooting steps

1. Check the Vehicle's Battery
2. Ensure the battery is fully charged and in good condition. A weak battery can cause various electrical issues
3. Inspect Fuses
4. Check the fuses related to the TCM and transmission system. A blown fuse can interrupt power to the TCM
5. Examine the TCM Power Relay
6. Locate the TCM power relay and inspect it for any signs of damage or corrosion. If necessary, test the relay using a multimeter or replace it with a known good relay
7. Inspect Wiring and Connectors
8. Check the wiring and connectors leading to the TCM and the power relay. Look for frayed wires, corrosion, or loose connections that could cause an open circuit
9. Test the TCM
10. If the relay and wiring appear to be in good condition, the TCM itself may be faulty. Use a scan tool to check for additional codes and monitor TCM data. If the TCM is not responding, it may need to be replaced
11. Check for Ground Issues
12. Ensure that the TCM has a good ground connection. A poor ground can lead to erratic behavior and trigger codes like P0885
13. Inspect the Transmission Control Circuit
14. Check the entire control circuit for any shorts or opens. This includes looking at the wiring harness and connectors for any signs of damage
15. Clear Codes and Test Drive
16. After performing the above checks and repairs, clear the trouble codes using a scan tool and take the vehicle for a test drive to see if the code returns
17. Refer to the vehicle's service manual for specific wiring diagrams and troubleshooting procedures related to the TCM and its power relay
18. Seek Professional Help
19. If the issue persists after performing these steps, it may be necessary to consult a professional mechanic or technician who has experience with transmission systems and OBD-II diagnostics. By following these steps, you should be able to identify and resolve the issue related to the P0885 code

Definition

Common causes

Common misdiagnoses

Troubleshooting steps

1. Check the Vehicle's Battery

2. Ensure the battery is fully charged and in good condition. A weak battery can cause various electrical issues

3. Inspect Fuses

4. Check the fuses related to the TCM and transmission system. A blown fuse can interrupt power to the TCM

5. Examine the TCM Power Relay

6. Locate the TCM power relay and inspect it for any signs of damage or corrosion. If necessary, test the relay using a multimeter or replace it with a known good relay

7. Inspect Wiring and Connectors

8. Check the wiring and connectors leading to the TCM and the power relay. Look for frayed wires, corrosion, or loose connections that could cause an open circuit

9. Test the TCM

10. If the relay and wiring appear to be in good condition, the TCM itself may be faulty. Use a scan tool to check for additional codes and monitor TCM data. If the TCM is not responding, it may need to be replaced

11. Check for Ground Issues

12. Ensure that the TCM has a good ground connection. A poor ground can lead to erratic behavior and trigger codes like P0885

13. Inspect the Transmission Control Circuit

14. Check the entire control circuit for any shorts or opens. This includes looking at the wiring harness and connectors for any signs of damage

15. Clear Codes and Test Drive

16. After performing the above checks and repairs, clear the trouble codes using a scan tool and take the vehicle for a test drive to see if the code returns

17. Refer to the vehicle's service manual for specific wiring diagrams and troubleshooting procedures related to the TCM and its power relay

18. Seek Professional Help

19. If the issue persists after performing these steps, it may be necessary to consult a professional mechanic or technician who has experience with transmission systems and OBD-II diagnostics. By following these steps, you should be able to identify and resolve the issue related to the P0885 code