P2551 fault code: Torque Management Request Input Signal 'B' High

P2551 means “Torque Management Request Input Signal 'B' High” — an extended powertrain range 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. P2551 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.

P25xxExtended powertrain range
MOT fail riskif the warning light stays on

What does P2551 mean?

P2551 is a powertrain code from the extended SAE range reported by your car’s engine control unit. It sits in the P25xx block, which covers extended powertrain range. The stored description is “Torque Management Request Input Signal 'B' High”. The code itself tells you which circuit or system tripped the fault — not always the exact part that failed.

Will P2551 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.
P2500Generator Lamp/L-Terminal Circuit Low P2501Generator Lamp/L-Terminal Circuit High P2502Charging System Voltage P2503Charging System Voltage Low P2504Charging System Voltage High P2505ECM/PCM Power Input Signal P2506ECM/PCM Power Input Signal Range/Performance P2507ECM/PCM Power Input Signal Low

P2551 — quick answers

Will P2551 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.