TCM Power Relay Sense Circuit Low
The P0890 code indicates that the Transmission Control Module (TCM) has detected a low voltage condition on the power relay sense circuit. This circuit monitors the voltage supplied to the TCM from the transmission control relay. When the voltage is below the expected threshold, the TCM sets this code. Common causes include a faulty relay, wiring issues, or a weak battery/charging system.
01. Most Common Causes
- Faulty transmission control relay
- Open or shorted wiring in the relay sense circuit
- Corroded or loose relay connections
- Weak battery or failing alternator
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Transmission shifting issues (harsh shifts, limp mode)
03. Step-by-Step Diagnosis
Step 1: Scan for codes and verify P0890 is present.
Step 2: Inspect the transmission control relay and its wiring for damage or corrosion.
Step 3: Test relay operation using a multimeter (check for 12V at the sense circuit).
Step 4: Check battery voltage and alternator output to ensure proper charging system.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended. Low voltage can cause erratic transmission behavior and may lead to further damage. Have it diagnosed promptly.
How much does it cost to fix?▼
Typically between $50 and $150 for parts and labor, depending on the cause (relay replacement vs. wiring repair).