P0891
TCM Power Relay Sense Circuit High
Transmission / control module power
Generic OBD-II
Medium
What it means
P0891 means the transmission control module (TCM) senses a high voltage on its power-relay sense circuit — the feedback line that tells the module whether its main power relay is on or off. When that feedback is out of range the TCM can't confirm its own power state, which may cause shifting problems or a protective limp mode. The engine still starts.
Medium
Can I keep driving? Engine starts and runs; the transmission may shift poorly or enter limp mode — have the power relay and its wiring checked soon.
Common symptoms
What you'll notice
- Check-engine or transmission warning light on
- Shifting problems or failure to change gears
- Transmission enters limp mode (reduced acceleration)
- Intermittent transmission faults
Common causes
Most likely first
- Short to voltage or open in the power-relay sense circuitLikely
- Faulty or stuck TCM power relayCommon
- Loose or corroded electrical connectionsCommon
- Faulty transmission control moduleLess often
How to diagnose & fix
Work through it in order
- Read freeze-frame data and inspect the relay and sense-circuit wiring and connectors.
- Compare the sense-circuit voltage against the relay's commanded state.
- Test the power relay for correct switching.
- Repair wiring or replace the relay; replace the TCM only if the circuit and relay test good. Clear and re-test.
FAQ
Quick answers
Is it safe to drive with P0891?+
The engine runs, but the transmission may shift poorly or enter limp mode. Get the relay and wiring checked before long trips.
Can I just clear P0891?+
It clears, but returns whenever the sense voltage is out of range again. Repair the relay or circuit first.
Related codes
Often seen with P0891
Read & clear P0891 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX