P0887
UniversalTCM Power Relay Control Circuit High
High SeverityThe P0887 code indicates that the Transmission Control Module (TCM) power relay control circuit is experiencing an abnormally high voltage reading. This electrical issue can cause the transmission to shift erratically, fail to shift, or enter a protective limp-home mode, severely affecting driveability.
⚠️ Before You Begin (Safety First)
Always disconnect the battery before performing any electrical work. Be cautious when working around hot engine components and transmission fluid. Ensure the vehicle is securely supported if lifting it.
Common Symptoms
- Check Engine Light (CEL) illuminated
- Transmission shifting problems (hard shifts, delayed shifts, no shifts)
- Transmission stuck in a single gear (limp mode)
- No communication with the TCM (in some cases)
- Vehicle may not start or move
Common Causes
- Faulty TCM power relay
- Short to voltage in the TCM power relay control circuit wiring
- Corroded or loose electrical connections
- Faulty TCM (less common, but possible)
- Blown fuse related to the TCM power circuit
Frequently reported on: All Makes
Diagnostic Steps
- Gather tools: Multimeter, wiring diagrams specific to your vehicle, basic hand tools.
- Visually inspect the TCM power relay and its connector for any signs of corrosion, damage, or loose connections.
- Locate the TCM power relay (often in the fuse box under the hood or dash) and check if it's operating correctly. You can try swapping it with a known good, identical relay from another non-critical system (e.g., horn relay, if applicable and the same type) for a quick test.
- Using a multimeter, test for proper voltage at the relay terminals according to your vehicle's wiring diagram. Look for constant power, switched power, and the control signal from the PCM/TCM.
- If the relay tests good, inspect the wiring between the relay and the TCM for any shorts to voltage or open circuits.
- Clear the code and test drive the vehicle after any repairs.
👨🔧 When to Call a Professional
If you lack experience with electrical diagnosis, especially using a multimeter, or if replacing the relay doesn't resolve the issue, it's best to consult a qualified automotive technician.
Commonly Asked Questions
What does P0887 mean?
It indicates a high voltage condition in the Transmission Control Module (TCM) power relay control circuit, signaling an electrical fault.
Can I drive with a P0887 code?
Driving is not recommended as it can lead to unpredictable shifting, transmission limp mode, or even potential transmission damage if ignored.
Is a P0887 code expensive to fix?
The cost varies. A simple relay replacement is often inexpensive, but diagnosing a complex wiring short or replacing the TCM can be more costly.
How do I test the TCM power relay?
You can test it by swapping it with a known good, identical relay, or by using a multimeter to check for continuity and proper voltage at its terminals as per your vehicle's wiring diagram.
What else could cause this code besides the relay?
Other causes include a short to voltage in the wiring harness, corroded or loose electrical connectors, a blown fuse, or a faulty Transmission Control Module (TCM) itself.