P0891 fault code: TCM Power Relay Sense Circuit High

P0891 means “TCM Power Relay Sense Circuit High” — a transmission fault in the powertrain. We do not yet publish verified symptoms, causes or repair steps for this code — treat an engine management light seriously and book a garage if you are unsure.

Can I DIY?

Not from this page. P0891 has no verified safety grade here yet, so we publish no DIY checks, repair steps or tool guidance for it. Treat an engine management light seriously and have the fault confirmed by a qualified garage.

Stop when it is safe to do so and arrange recovery if the engine management light is flashing, the car judders, overheats or loses power, or you can smell fuel or exhaust fumes inside the car.

P08xxTransmission
MOT fail riskif the warning light stays on

What does P0891 mean?

P0891 is a generic (SAE standard) powertrain code reported by your car’s engine control unit. It sits in the P08xx block, which covers transmission. The stored description is “TCM Power Relay Sense Circuit High”. The code itself tells you which circuit or system tripped the fault — not always the exact part that failed.

Will P0891 fail an MOT?

An illuminated engine management light is a Major defect at MOT since 2018 — an automatic fail until the fault is repaired and the light stays off. Clearing the code without fixing the cause is not a repair.

Before booking your test, check what usually fails on your car: see our MOT pass rates by make and model, built from 33.1 million DVSA tests.

Related guides

Car diagnostic test cost: compare the scopeUK booking marketplaces currently publish diagnostic averages of about £52–£65. Engine management light on: steady or flashing?A steady engine management light means the computer has stored a fault. Drive with caution and get the code read. A flashing light is different — stop when it is safe.
P0800Transfer Case Control System (MIL Request) P0801Reverse Inhibit Control Circuit P0802Transmission Control System MIL Request Circuit/Open P08031-4 Upshift (Skip Shift) Solenoid Control Circuit P08041-4 Upshift (Skip Shift) Lamp Control Circuit P0805Clutch Position Sensor Circuit P0806Clutch Position Sensor Circuit Range/Performance P0807Clutch Position Sensor Circuit Low

P0891 — quick answers

Will P0891 fail my MOT?

An illuminated engine management light is a Major defect at MOT since 2018 — an automatic fail until the fault is repaired and the light stays off. Clearing the code without fixing the cause is not a repair.

Fault-code identifiers are standard diagnostic facts. Their explanations and diagnostic guidance on this site are original editorial summaries, not reproduced SAE wording. MOT defect rules reflect the DVSA MOT inspection manual (2026). This page is general guidance for UK drivers, not a substitute for a professional diagnosis.