TCM Power Relay Control Circuit High
The P0887 code indicates that the Transmission Control Module (TCM) has detected a high voltage condition in the power relay control circuit. This circuit supplies power to the TCM and related transmission solenoids. A high voltage reading typically points to a short to voltage, a faulty relay, or a problem with the TCM itself. This can cause erratic transmission behavior or prevent the vehicle from shifting properly.
01. Most Common Causes
- Faulty TCM power relay
- Short to voltage in the relay control circuit wiring
- Corroded or damaged relay connector
- Faulty TCM (less common)
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Transmission stuck in limp mode or fails to shift
- Harsh or delayed shifting
- Transmission overheating or slipping
03. Step-by-Step Diagnosis
Step 1: Scan for additional codes and check freeze frame data.
Step 2: Inspect the TCM power relay and its wiring for damage, corrosion, or shorts.
Step 3: Test relay control circuit voltage with a multimeter; compare to manufacturer specs.
Step 4: If wiring and relay are okay, test TCM power and ground circuits; replace TCM if necessary.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
No, it is not recommended. The transmission may enter limp mode, causing reduced performance and potential damage.
How much does it cost to fix?▼
Typically $50-$150 for relay and wiring repairs; TCM replacement can cost $500-$1000.