TCM Power Relay Sense Circuit Range/Performance
P0889 indicates the transmission control module (TCM) is detecting a voltage issue in its power relay sense circuit, meaning the TCM isn't receiving proper electrical supply or feedback. This electrical malfunction can prevent the transmission from shifting correctly and disable safety systems like traction control.
What You Might Notice
- Check engine light (MIL) illuminated
- Erratic or delayed transmission shifts
- Transmission stuck in one gear or limp mode
- Electronic traction control disabled
- ABS system disabled or inoperative
Most Common Causes
- 1
Blown TCM power fuse
A blown fuse in the TCM power supply circuit prevents adequate voltage from reaching the transmission control module. Check the fuse box for a blown fuse labeled for TCM or transmission power.
- 2
Faulty TCM power relay
The relay that supplies power to the TCM may be stuck open, corroded, or defective, interrupting voltage delivery. This is one of the most common causes of this code.
- 3
Corroded or loose battery terminals
Poor electrical connections at the battery terminals can reduce available voltage throughout the vehicle's electrical system, including to the TCM.
- 4
Damaged TCM connector or wiring
Corroded, broken, or loose connectors and wiring harnesses between the battery, relay, fuses, and TCM prevent proper power delivery to the module.
How to Diagnose It
- 1
Check Blown TCM power fuse — A blown fuse in the TCM power supply circuit prevents adequate voltage from reaching the transmission control module. Check the fuse box for a blown fuse labeled for TCM or transmission power.
- 2
Check Faulty TCM power relay — The relay that supplies power to the TCM may be stuck open, corroded, or defective, interrupting voltage delivery. This is one of the most common causes of this code.
- 3
Check Corroded or loose battery terminals — Poor electrical connections at the battery terminals can reduce available voltage throughout the vehicle's electrical system, including to the TCM.
- 4
Check Damaged TCM connector or wiring — Corroded, broken, or loose connectors and wiring harnesses between the battery, relay, fuses, and TCM prevent proper power delivery to the module.
How to Fix It
- 1
Replace TCM power fuse
Locate the TCM power fuse in the vehicle's fuse box (check owner's manual or fuse diagram), remove it, and install a new fuse of the same amperage. If it blows again, investigate the circuit for a short.
- 2
Replace TCM power relay
Remove the faulty TCM power relay from the relay panel and install a new relay of the same part number. Test transmission operation after installation.
- 3
Clean and tighten battery terminals
Disconnect the battery, clean both terminals and cable ends with a wire brush to remove corrosion, and reconnect them securely. Ensure posts are tight and free of white or blue oxidation.
- 4
Repair TCM connector and wiring
Inspect the TCM power connector, relay connector, and all associated wiring for corrosion, loose pins, or breaks. Repair, resolder, or replace damaged connectors and wiring as needed.
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