P0931 fault code: Gear Shift Lock Solenoid Control Circuit High High severity

P0931 means “Gear Shift Lock Solenoid Control Circuit High” — a transmission fault in the powertrain. Limp mode exists to protect the gearbox — get it scanned promptly. Typical UK repair cost: £80–£2500 depending on the underlying cause.
HighSeverity
P09xxTransmission
£80–2500Typical UK repair cost
MOT fail riskif the warning light stays on

What does P0931 mean?

P0931 is a generic (SAE standard) powertrain code reported by your car’s engine control unit. It sits in the P09xx block, which covers transmission. The stored description is “Gear Shift Lock Solenoid Control Circuit High”. The code itself tells you which circuit or system tripped the fault — not always the exact part that failed, which is why a short diagnosis pays for itself before replacing components.

Symptoms you may notice

  • Harsh or delayed gear changes
  • Gearbox stuck in limp mode (one gear only)
  • Slipping under acceleration
  • Transmission warning light or flashing gear indicator

Most common causes

  1. Low or degraded transmission fluid
  2. Faulty shift solenoid or speed sensor
  3. Worn clutch packs in automatics
  4. Wiring faults to the transmission control module

How to diagnose P0931 yourself

  1. Check transmission fluid level and condition where a dipstick is fitted
  2. Read live gear ratio and solenoid data with a full-system scanner
  3. Investigate wiring and connectors at the gearbox before internal repairs
Tools that read and clear P0931

A basic code reader confirms the fault; a full-system scanner shows the live data you need for the steps above.

Will P0931 fail an MOT?

The gearbox itself is not MOT-tested, but a transmission fault light that also lights the engine management lamp will fail. Fluid leaks marked as excessive are also a fail.

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.

Typical UK repair costs

OutcomeTypical cost (parts + labour)
DIY: read code + basic checks£0 (scanner assumed)
Independent garage diagnosis£30–£60
Typical repair range for this fault£80–£2500
Main dealer equivalent£120–£4500

Costs are indicative UK ranges for independent garages in 2026. Main dealers typically charge 40–80% more.

Diagnose the symptom, then price the repair

Car diagnostic test cost UK (2026): scan vs actual diagnosis£40–£100 is typical for an independent first assessment — but a code read is not the same as finding the cause.
P0900Clutch Actuator Circuit/Open P0901Clutch Actuator Circuit Range/Performance P0902Clutch Actuator Circuit Low P0903Clutch Actuator Circuit High P0904Gate Select Position Circuit P0905Gate Select Position Circuit Range/Performance P0906Gate Select Position Circuit Low P0907Gate Select Position Circuit High

P0931 — quick answers

Is it safe to drive with P0931?

Limp mode exists to protect the gearbox — get it scanned promptly. Continued driving with slipping gears multiplies the repair bill.

Will P0931 clear itself?

If the underlying fault stops occurring, most ECUs extinguish the light after around 40 healthy warm-up cycles — but the code stays stored as history. Fix the cause, clear it with a scanner, then confirm it stays away over a full drive cycle.

How much does it cost to fix P0931 in the UK?

Typically £80–£2500 at an independent garage depending on which cause you confirm. Diagnosing it yourself with a scanner avoids a £30–£60 diagnostic fee and stops parts being replaced on guesswork.

Will P0931 fail my MOT?

The gearbox itself is not MOT-tested, but a transmission fault light that also lights the engine management lamp will fail. Fluid leaks marked as excessive are also a fail.

Code definitions follow the SAE J2012 standard. 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.