P0885 TCM Power Relay Control Circuit/Open

P0885 points to a TCM power relay control circuit or open-circuit fault. The controller cannot properly command the relay that feeds transmission electronics.

Code details

Generic OBD-II · P0

System: Transmission
Code type: Generic (SAE / ISO controlled)
Standard: SAE J2012 / ISO 15031-6

Diagnostic boundary

A diagnostic trouble code reports that a monitored test failed. It does not prove one specific part is bad, and manufacturer logic can add vehicle-specific conditions.

Do not replace the TCM before checking the relay control circuit; an open relay path can make a good module appear offline.

Symptoms of P0885

Harsh, delayed, or slipping shifts, or being stuck in one gear.
Check-engine light, sometimes with limp-home mode.
Flaring RPM or a shudder under load.

Common causes of P0885

Low or degraded transmission fluid.
A failing speed sensor, shift solenoid, or pressure-control circuit.
Wiring, connector, or internal hydraulic/mechanical faults.

Useful checks before replacing parts

Check relay coil power, control ground or driver circuit, fuse feed, relay socket terminals, and command state.
Compare relay command with actual relay output voltage and TCM power input at key-on and during cranking.
Inspect wiring damage, corrosion, water intrusion, and related TCM power input or communication codes.

Related OBD-II codes

These nearby transmission entries can help compare wording and pin down the fault area.