Why does my car only stall when hot with P0335?

Because that is how crankshaft position sensors typically fail. The sensor contains a winding or a semiconductor element whose behaviour changes with temperature, and as it ages it develops a fault that only appears once heat-soaked. The engine runs perfectly from cold, cuts out after twenty minutes or so, refuses to restart while hot, and then starts perfectly after standing for half an hour. That pattern is close to diagnostic on its own, and it is worth describing to the garage exactly as it happens.

Can a car run without a crankshaft position sensor?

On most engines, no. The crank signal is how the control unit knows where every piston is, and without it there is no way to decide when to inject fuel or fire a spark, so the engine cranks and never catches. A small number of engines can limp on the camshaft position signal alone if the crank signal is lost while running, which is why some cars keep going for a short while before dying, but none will start from cold without it.

Will P0335 fail an MOT?

Yes, twice over in most cases. The engine management lamp is a major defect for petrol cars first used from 1 July 2003 and diesels from 1 July 2008, with 371,859 recorded failures. On top of that, a car that stalls during the test cannot complete the emissions check, and an incomplete emissions test is itself a major failure. A car that will not start cannot be tested at all.

Is a crankshaft sensor expensive to replace?

The part is generally one of the cheaper engine sensors. What varies enormously is getting at it. On some engines it is visible and accessible from above and the job takes minutes; on others it sits behind the starter motor, above the sump or between the engine and the bulkhead, and reaching it takes a substantial part of a day. Ask the garage where the sensor is on your specific engine before assuming the quote is unreasonable.

Powertrain code · standard

P0335Crankshaft position sensor signal missing

Standard definition: Crankshaft Position Sensor "A" Circuit Malfunction

Last updated 27 July 2026

Quick answer

The engine control unit has lost the signal that tells it where the crankshaft is and how fast it is turning. Without it the unit cannot time the ignition or the injection, so the engine usually will not start or will cut out.

How the car works this out

A toothed ring on the crankshaft or flywheel passes a sensor, which produces a pulse for each tooth and a distinctive gap where teeth are deliberately missing, giving the control unit an absolute reference for crank position. Everything else — when to fire each injector, when to spark — is built on that. P0335 is set when the pulse train is absent or unrecognisable. Because the engine cannot run without it, this code is far more often found on a car that will not start than on one being investigated for a lamp.

What you might notice

Engine cranks over normally but will not fire
Cutting out without warning while driving, then restarting after a wait
Stalling when hot, with the car refusing to restart until it has cooled — the classic pattern
Rev counter dropping to zero or behaving erratically while the engine is running
Rough running and misfiring at higher revs

What causes it

Most likely first. A code names the check that failed, not the part that failed it, so more than one of these can produce the same number.

1A failed sensor, very often one that only fails when hotCommon
How to check: If the car stalls when hot and restarts once cool, that pattern alone points at the sensor. A garage can also warm the sensor gently and watch the live signal drop out.
2A damaged, corroded or oil-soaked connectorCommon
How to check: Unplug and inspect. These sensors sit low on the engine near the sump and gearbox, where oil and road spray reach them.
3Chafed or broken wiring in the sensor loomCommon
4Debris, swarf or oil sludge on the sensor tip, bridging the gap to the tone ringPossible
How to check: Remove the sensor and look at its tip. A magnetic sensor collects metal particles from the gearbox and engine over the years.
5A damaged tone or reluctor ring, with chipped or bent teethPossible
6A timing belt or chain that has jumped, so the crank and cam signals no longer correlateLess common
How to check: Check whether a camshaft position code is stored alongside. Two correlated timing codes together change the diagnosis completely and need investigating before the engine is cranked again.

What to do about it

1Note the pattern before you go to the garage. A car that stalls when hot and restarts when cool is describing a heat-sensitive crank sensor, and that history is worth more than an hour of workshop time.
2Do not keep cranking a car that will not start. You will flatten the battery, cook the starter, and on a direct-injection engine wash the bores with fuel.
3Have the connector and the sensor tip inspected before ordering parts, and check for oil contamination, which is common on sensors mounted near a leaking seal.
4Fit a manufacturer-quality sensor. Crank sensors are a well-known area for cheap copies failing quickly, and the labour to get at them is often the larger part of the job.
5Ask whether the car needs a crank sensor relearn afterwards. Many engines require an adaptation procedure so the control unit can characterise the new sensor's signal, and the misfire monitor may not work correctly until it has run.

Can you keep driving?

Not sensibly, and often not at all. An engine that cuts out without warning takes the power steering assistance and the brake servo with it, which is dangerous at a junction or on a slip road. Where the car will not start at all the decision is made for you. Either way, this is a recover-it rather than a nurse-it-home fault.

Will it fail an MOT?

The lamp is a major defect and one of 371,859 recorded failures against an illuminated engine malfunction indicator lamp. The bigger issue on test day is whether the car can be tested at all: the emissions check needs a sustained steady idle and a period at a raised engine speed, and an engine that stalls partway through cannot complete it. An emissions test that cannot be completed is recorded as a major failure separately from the lamp.

The light this turns on

Engine management lightThe engine management system has found a fault it cannot correct and has stored a code for it. The car will usually still drive, but an illuminated engine light is an automatic MOT failure on petrol cars first used from 1 July 2003 and diesels from 1 July 2008.

Common questions

Why does my car only stall when hot with P0335?: Because that is how crankshaft position sensors typically fail. The sensor contains a winding or a semiconductor element whose behaviour changes with temperature, and as it ages it develops a fault that only appears once heat-soaked. The engine runs perfectly from cold, cuts out after twenty minutes or so, refuses to restart while hot, and then starts perfectly after standing for half an hour. That pattern is close to diagnostic on its own, and it is worth describing to the garage exactly as it happens.
Can a car run without a crankshaft position sensor?: On most engines, no. The crank signal is how the control unit knows where every piston is, and without it there is no way to decide when to inject fuel or fire a spark, so the engine cranks and never catches. A small number of engines can limp on the camshaft position signal alone if the crank signal is lost while running, which is why some cars keep going for a short while before dying, but none will start from cold without it.
Will P0335 fail an MOT?: Yes, twice over in most cases. The engine management lamp is a major defect for petrol cars first used from 1 July 2003 and diesels from 1 July 2008, with 371,859 recorded failures. On top of that, a car that stalls during the test cannot complete the emissions check, and an incomplete emissions test is itself a major failure. A car that will not start cannot be tested at all.
Is a crankshaft sensor expensive to replace?: The part is generally one of the cheaper engine sensors. What varies enormously is getting at it. On some engines it is visible and accessible from above and the job takes minutes; on others it sits behind the starter motor, above the sump or between the engine and the bulkhead, and reaching it takes a substantial part of a day. Ask the garage where the sensor is on your specific engine before assuming the quote is unreasonable.

Check any vehicle's MOT history

Free, instant, and straight from DVSA records. No sign-up.