TCM Power Relay Sense Circuit Malfunction
The P0888 code indicates a fault in the transmission control module (TCM) power relay sense circuit. This circuit monitors the voltage supplied to the TCM via the power relay. When the TCM detects an unexpected voltage level (too high, too low, or absent) on the sense circuit, it sets this code. Common causes include a faulty relay, blown fuse, wiring issues, or a failing TCM. This can lead to transmission shifting problems or no start conditions.
01. Most Common Causes
- Faulty TCM power relay
- Blown fuse in TCM power circuit
- Damaged wiring or poor connection in relay sense circuit
- Corroded relay socket terminals
- Failing TCM
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Transmission shifting erratically or stuck in gear
- Vehicle may not start or stalls
- Reduced fuel economy
- Transmission warning light on
03. Step-by-Step Diagnosis
Step 1: Use a scan tool to confirm P0888 and check for other related codes.
Step 2: Inspect the TCM power relay and fuse; test relay operation with a multimeter.
Step 3: Check voltage at the TCM power relay sense circuit pin; should be battery voltage with key on.
Step 4: Visually inspect wiring and connectors for damage, corrosion, or loose connections.
Step 5: If all else is good, test the TCM for internal faults or replace it.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
No, it is not recommended. The transmission may shift unpredictably or fail to operate, and the vehicle could stall, posing a safety risk.
How much does it cost to fix?▼
Typically $50-$150 for relay/fuse replacement, but if the TCM needs replacement, costs can exceed $500.