TCM Power Relay Sense Circuit Low
P0890 indicates the transmission control module (TCM) is detecting insufficient voltage in its power relay sense circuit. This electrical fault prevents the TCM from receiving proper power supply signals, which can cause transmission and traction control malfunctions.
What You Might Notice
- Check engine light illuminated
- Electronic traction control disabled or inoperative
- Erratic or delayed transmission shift patterns
- Transmission fails to shift properly
- ABS system disabled
Most Common Causes
- 1
Blown TCM power relay fuse
A blown fuse in the TCM power relay circuit prevents adequate voltage from reaching the transmission control module, triggering this code.
- 2
Faulty TCM power relay
A defective relay fails to supply consistent voltage to the TCM sense circuit, causing the module to detect low voltage conditions.
- 3
Corroded or loose battery connections
Poor electrical connections at the battery terminals or ground points reduce available voltage throughout the vehicle's electrical system, including TCM supply lines.
- 4
Damaged wiring or connectors in TCM power circuit
Broken wires, corroded terminals, or loose connectors in the TCM power supply harness can cause voltage drop and sense circuit failures.
How to Diagnose It
- 1
Check Blown TCM power relay fuse — A blown fuse in the TCM power relay circuit prevents adequate voltage from reaching the transmission control module, triggering this code.
- 2
Check Faulty TCM power relay — A defective relay fails to supply consistent voltage to the TCM sense circuit, causing the module to detect low voltage conditions.
- 3
Check Corroded or loose battery connections — Poor electrical connections at the battery terminals or ground points reduce available voltage throughout the vehicle's electrical system, including TCM supply lines.
- 4
Check Damaged wiring or connectors in TCM power circuit — Broken wires, corroded terminals, or loose connectors in the TCM power supply harness can cause voltage drop and sense circuit failures.
How to Fix It
- 1
Replace TCM power relay fuse
Locate the TCM power relay fuse in the vehicle's fuse box (consult owner's manual for location), inspect it for burning or breakage, and replace with the correct amperage rating fuse.
- 2
Replace TCM power relay
Access the relay from the fuse/relay box, pull out the old relay, and install a new OEM or equivalent relay in the same position.
- 3
Clean and secure battery terminals
Disconnect battery negative terminal, clean corrosion from both battery terminals and ground connections with a wire brush, then reconnect firmly to ensure proper voltage distribution.
- 4
Inspect and repair TCM wiring harness
Visually trace the TCM power supply wiring from the relay to the transmission control module, checking for damaged insulation, broken wires, or corroded connectors. Repair or replace damaged sections and ensure all connectors are fully seated.
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