Is a P0016 code serious?

It is the most serious code in the misfire and timing family. It means the camshaft and crankshaft are no longer in the relationship the engine was built with, and the commonest reason for that is a timing chain that has stretched or a belt that has slipped. A chain in that state can skip further at any moment, and on an interference engine — which is nearly all of them — that drives valves into pistons and can write off the engine. It can also be caused by something as minor as a failing sensor, but you cannot tell which from the driving seat, so it needs checking before the car is used.

Can I drive with a P0016 code?

You should not. If the cause is mechanical, every mile is a chance for the chain or belt to skip further and destroy the engine, and the repair goes from a timing kit to a cylinder head or a replacement engine. If there is a rattle for the first seconds after a cold start, hard starting, or the car has dropped into limp mode, have it recovered rather than driven at all.

Can a camshaft sensor cause P0016?

Yes. The code is a comparison between two sensor signals, so a camshaft or crankshaft sensor that reports inaccurately can set it with the timing drive in perfect condition. That makes the sensor worth testing early, because it is much the cheaper answer. What it does not justify is replacing the sensor and driving on if the code returns, because a chain that is genuinely stretching produces the same code and will not wait.

Will P0016 fail an MOT?

Yes, and potentially twice. An illuminated engine management lamp is a major defect for petrol cars first used on or after 1 July 2003 and diesels from 1 July 2008. Beyond that, the emissions test requires the engine to be held at a fast idle of around 2,500 to 3,000 rpm, and a car in limp mode may not reach it. A test that cannot be completed is recorded as a major failure of its own.

Powertrain code · standard

P0016Camshaft and crankshaft are out of step, bank 1

Standard definition: Crankshaft Position - Camshaft Position Correlation (Bank 1 Sensor A)

Last updated 27 July 2026

Quick answer

The control unit has compared where the camshaft says it is against where the crankshaft says it is, and found the two do not line up. Of all the misfire and valve timing codes, this is the one to take seriously, because the usual cause is a timing chain or belt that has stretched or slipped, and what comes after slipping is valves meeting pistons.

How the car works this out

Both the crankshaft and the camshaft carry a toothed or slotted wheel read by a sensor, and each wheel has a reference feature so the control unit knows exactly where in the rotation it is. On a healthy engine the two signals hold a fixed relationship, because the camshaft is driven from the crankshaft by a chain, a belt or gears. The unit checks that relationship at start-up and continuously afterwards, allowing for whatever the variable valve timing has been commanded to do, and stores the correlation code if the measured offset falls outside tolerance. Because it is a comparison of two sensors, it can be triggered by a genuine mechanical change in the timing, by a phaser that has moved when it should have been locked, or by either sensor or its trigger wheel misreporting. Only one of those is cheap, and you cannot tell which from the driving seat.

What you might notice

A rattle from the timing drive for the first second or two after a cold start, which is the chain slapping before the tensioner pressurises
Long cranking before the engine catches, or a car that will not start at all
Rough running, a serious loss of power, or the engine dropping into limp mode
The engine management lamp on, often with the car noticeably slower than usual
In the worst case an engine that spins over freely and never fires, because the timing has jumped several teeth

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 stretched timing chain, or a failed chain tensioner or guide letting the chain go slackCommon
How to check: Listen at a cold start from outside the car. A rattle lasting a second or two that then quietens is the classic sign. A garage can also compare the live camshaft and crankshaft angles and, on many engines, read chain wear from how far the tensioner has extended.
2A timing belt that has slipped a tooth, or, on engines using a belt that runs in engine oil, one that has degraded and stretchedCommon
How to check: Check when the belt was last changed and against which interval. Several manufacturers shortened the interval on wet-belt engines after the originals proved optimistic.
3A camshaft phaser that has worn internally, or whose centre bolt has loosened, letting the camshaft move independently of the drivePossible
4A failing camshaft or crankshaft position sensor giving a signal that is present but not accuratePossible
How to check: Far cheaper to rule out than the alternative, and worth doing first if there is no rattle, no hard starting and no history of missed services.
5A cracked, slipped or damaged trigger wheel, or a sheared locating key on the crankshaftLess common
6An engine reassembled a tooth out after previous timing workLess common
How to check: If the code appeared immediately after a cambelt or chain job, this is the first thing to check, and the garage that did the work should be the one checking it.
7Very low oil pressure, on engines whose chain tensioner is fed by oil and only holds the chain tight once pressure buildsLess common

What to do about it

1Listen to it from cold, standing outside the car with the bonnet up. A rattle in the first seconds after start-up moves this straight to the top of the urgent list.
2Stop driving it if there is a rattle, if the engine is in limp mode, or if it has become hard to start. A chain stretched far enough to set a correlation code can skip a tooth at any time, and on an interference engine that bends valves.
3Have the actual cam and crank timing verified against the manufacturer's data. This is not a code to guess at, and a proper check is quick for a garage with the right information.
4Say whether any timing work has been done recently, and when the belt or chain was last replaced. It reframes the whole diagnosis.
5Do not simply fit a camshaft sensor because it is the cheap part. A sensor is a genuine possibility and worth testing, but a sensor swap that quietens the code for a fortnight while a chain carries on stretching is the most expensive kind of false economy.

Can you keep driving?

Treat this as a stop. It might be nothing worse than a sensor, in which case nothing bad is happening, but you cannot tell that from behind the wheel and the alternative is a timing chain about to jump. On an interference engine, which covers very nearly everything built in the last thirty years, a jumped chain drives valves into pistons and turns a chain kit into an engine rebuild. Have it recovered rather than driven, especially if there is a rattle at start-up.

Will it fail an MOT?

Two separate routes to a failure certificate. The lamp is a major defect on petrol cars first used from 1 July 2003 and diesels from 1 July 2008, which alone accounts for 371,859 failures in the DVSA data behind this site. The second route is more particular to this code: the petrol emissions check requires the engine to be held at a fast idle, roughly 2,500 to 3,000 rpm, while the readings settle, and a car in limp mode may simply refuse to rev that far. An emissions test that cannot be completed is a major failure in its own right, and if the engine will not start the test cannot begin at all.

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

Is a P0016 code serious?: It is the most serious code in the misfire and timing family. It means the camshaft and crankshaft are no longer in the relationship the engine was built with, and the commonest reason for that is a timing chain that has stretched or a belt that has slipped. A chain in that state can skip further at any moment, and on an interference engine — which is nearly all of them — that drives valves into pistons and can write off the engine. It can also be caused by something as minor as a failing sensor, but you cannot tell which from the driving seat, so it needs checking before the car is used.
Can I drive with a P0016 code?: You should not. If the cause is mechanical, every mile is a chance for the chain or belt to skip further and destroy the engine, and the repair goes from a timing kit to a cylinder head or a replacement engine. If there is a rattle for the first seconds after a cold start, hard starting, or the car has dropped into limp mode, have it recovered rather than driven at all.
Can a camshaft sensor cause P0016?: Yes. The code is a comparison between two sensor signals, so a camshaft or crankshaft sensor that reports inaccurately can set it with the timing drive in perfect condition. That makes the sensor worth testing early, because it is much the cheaper answer. What it does not justify is replacing the sensor and driving on if the code returns, because a chain that is genuinely stretching produces the same code and will not wait.
Will P0016 fail an MOT?: Yes, and potentially twice. An illuminated engine management lamp is a major defect for petrol cars first used on or after 1 July 2003 and diesels from 1 July 2008. Beyond that, the emissions test requires the engine to be held at a fast idle of around 2,500 to 3,000 rpm, and a car in limp mode may not reach it. A test that cannot be completed is recorded as a major failure of its own.

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