P0846 fault code: Transmission Fluid Pressure Sensor/Switch 'B' Circuit Range/Performance High severity

P0846 means “Transmission Fluid Pressure Sensor/Switch 'B' Circuit Range/Performance” — 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

P08xxTransmission

£80–2500Typical UK repair cost

MOT fail riskif the warning light stays on

What does P0846 mean?

P0846 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 “Transmission Fluid Pressure Sensor/Switch 'B' Circuit Range/Performance”. 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

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

How to diagnose P0846 yourself

Check transmission fluid level and condition where a dipstick is fitted
Read live gear ratio and solenoid data with a full-system scanner
Investigate wiring and connectors at the gearbox before internal repairs

Tools that read and clear P0846

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

Topdon OBD2 scannersTopdon diagnostic scanners with full-system readouts
XTOOL diagnostic toolsXTOOL code readers for petrol and diesel cars
Autel UK testersAutel professional-grade diagnostic testers

Will P0846 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

Outcome	Typical 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.

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

P0846 — quick answers

Is it safe to drive with P0846?

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

Will P0846 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 P0846 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 P0846 fail my MOT?