TCM Power Relay Sense Circuit Range/Performance
The P0889 code indicates that the Transmission Control Module (TCM) has detected an abnormal voltage reading from the power relay sense circuit. This circuit monitors the voltage supplied to the TCM from the transmission control relay. A range/performance issue means the voltage is either too high, too low, or intermittent, which can disrupt TCM operation and affect transmission shifting.
1. Symptoms You Will Notice
- Check Engine Light illuminated
- Transmission shifting erratically or stuck in limp mode
- No start or engine cranks but won't start (if TCM controls starter relay)
- Transmission warning light on
2. Most Common Causes
- Faulty transmission control relay
- Blown fuse or wiring issues in the relay circuit
- Corroded or loose connectors at the TCM or relay
- Faulty TCM (rare)
3. Step-by-Step Diagnosis
Step 1: Scan for additional codes and check freeze frame data.
Step 2: Inspect the transmission control relay and its fuse; test relay operation with a multimeter.
Step 3: Check wiring and connectors for damage, corrosion, or loose connections between the relay and TCM.
Step 4: Measure voltage at the TCM power relay sense pin; compare to manufacturer specifications.
Step 5: If all else is okay, test the TCM for internal faults (requires professional scan tool).
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended. The transmission may shift poorly or enter limp mode, which can cause unsafe driving conditions and potential transmission damage.
How much does it cost to fix?▼
Typically $50-$150 for relay and fuse replacement; more if wiring repairs or TCM replacement is needed.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.