The TCM power relay control circuit exists between the battery and the transmission control module, and protects the transmission’s computer from voltage irregularities. It also allows for a self test when the ignition key is turned on. If there is a high-voltage signal detected on this circuit, a P0887 DTC will be saved.
How Serious is the Code?
The P0887 diagnostic trouble code is very serious, because it means the TCM is in danger of being damaged from unusually high voltage. This can result in a number of transmission problems including delayed shifts, harsh shifts and even engine stalling.
Symptoms of a P0887 include:
- Harsh or erratic transmission behavior
- Delayed shifting
- Engine may stall unexpectedly
- Shift interlock failure
- Malfunctioning speedometer
- TCM or ECU power relay failure
- Blown/corroded fuse
- Fusible link failure
- Damaged connectors and/or wiring
- ECU programming/function problem
How to Diagnose the Code?
When you’re trying to figure out what is causing a P0887 OBDII trouble code, it’s important to first check the voltage output of both the alternator and battery (these are often the cause of this OBD2 code). If both of those check out, then you’ll need to test all of the relays, fuses and fusible links. If you can’t find anything wrong there, then check the wiring and connectors for signs of damage and corrosion. When you test the TCM power relay connector, if no voltage shows up, then there is a problem somewhere within the circuit. If there is voltage, but the code still shows up, then there is likely a problem with either the ECU programming or the ECU itself.
What Repairs Will Fix P0887?
- Repair or replace damaged wiring/connectors
- Replace the power relay
- Replace the blown fuse(s)
- Replace the fusible link
- Reprogram or replace the ECU
- P0700 – Transmission Control System Malfunction
- P0701 – Transmission Control System Range/Performance
- P0702 – Transmission Control System Electrical
- P0800 – TCM Power Input Signal Malfunction