What is camshaft position sensor B?

It is the second camshaft sensor on a bank, which on almost every twin-cam engine reads the exhaust camshaft. Sensor A reads the intake camshaft and is the one the engine uses to work out which stroke each cylinder is on. Sensor B exists because engines with variable timing on both camshafts need to measure both, and it feeds the control of the exhaust phaser. That is why losing sensor B costs you exhaust valve timing control rather than the ability to start.

Can I drive with a P0365 code?

Yes, in the short term. The engine keeps its stroke synchronisation from the other camshaft sensor, so it starts and runs normally in that respect. What you lose is variable control of the exhaust valve timing, which usually parks at a default position, leaving the car feeling flat with a slightly lumpy idle and marginally worse economy. It is not damaging, but it will not repair itself and the lamp will fail an MOT.

What is the difference between P0340 and P0365?

They are the same kind of circuit fault on different sensors of the same bank. P0340 concerns sensor A, normally the intake camshaft, which is the signal the engine uses to synchronise injection and ignition to the four-stroke cycle. P0365 concerns sensor B, normally the exhaust camshaft, which is used to control the exhaust phaser. That is why P0340 typically gives long cranking, stalling and sometimes a no-start, while P0365 usually just gives a flat engine and a poor idle.

Will P0365 fail an MOT?

Yes. The 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, and it fails the car whatever the engine sounds like. There is a second route as well: with the exhaust phaser stuck at its default position the hydrocarbon and lambda readings both shift, and both are measured at the fast idle emissions test.

Powertrain code · standard

P0365No usable signal from the second camshaft sensor, bank 1

Standard definition: Camshaft Position Sensor B Circuit (Bank 1)

Last updated 27 July 2026

Quick answer

The bank one exhaust camshaft sensor, the second of the two sensors on a twin-cam cylinder head, is not producing a usable signal. Because that sensor's main job is feeding the exhaust valve timing control rather than telling the engine which stroke it is on, the symptoms are usually milder than a P0340: a lumpy idle and a flat engine rather than a car that will not start.

How the car works this out

The monitoring is identical to any other camshaft sensor circuit — the control unit looks for pulses in the expected pattern and stores a code when they are missing or unusable — but the consequences are different because of what the signal is used for. The engine takes its stroke synchronisation from the camshaft designated A, normally the intake camshaft, so losing the B sensor does not usually stop the engine knowing where it is. What it does stop is closed-loop control of the exhaust phaser, because the unit can no longer measure what that camshaft is doing. Most engines respond by parking the exhaust phaser at its default position and leaving it there, which is why the car runs but runs flatly.

What you might notice

A lumpy or slightly unstable idle
A flat, unresponsive engine with less low-down pull than usual
Slightly worse fuel consumption
The engine management lamp on, often with a variable valve timing code such as P0014 stored alongside
Rarely, a starting problem, because this sensor is not the one the engine synchronises from

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.

1The sensor itselfCommon
How to check: Compare live data for both camshaft sensors. One reading nothing while the other reads normally makes the case immediately.
2Oil in the connector, wicked along the wires from a leaking sensor seal or cam cover gasketCommon
3Chafed or heat-damaged wiring between the sensor and the control unitPossible
4A damaged trigger wheel on the exhaust camshaft, or debris packed into itPossible
5A loose sensor mounting bolt changing the air gapLess common
6On engines where the high-pressure fuel pump is driven from this camshaft, wear at the follower or the lobe affecting what the sensor seesLess common
How to check: Fuel pressure codes stored alongside are the clue. Have the follower inspected while the cam cover is off, since that wear damages the camshaft if it is left.

What to do about it

1Check the connector for oil before buying a sensor. It is the same failure as on the intake side and just as common.
2Have the live data for both camshaft sensors compared. Having a working sensor on the same engine to compare against makes this one of the easier faults to confirm.
3Look at what else is stored. A variable valve timing code for the exhaust camshaft alongside this one is consistent and expected; a correlation code such as P0017 is not, and moves the investigation towards the timing drive.
4Fix the oil leak that caused it, if there was one, or the replacement sensor will go the same way.

Can you keep driving?

Briefly, gently

This is one of the milder camshaft sensor faults. The engine still knows which stroke it is on, so it starts and runs; it simply loses the ability to vary the exhaust valve timing and sits at a default setting. Expect it to feel flat and drink a little more fuel. It is not urgent, but it will not fix itself and the car cannot pass an MOT while the lamp is on.

Will it fail an MOT?

A default exhaust phaser position is not a neutral setting as far as the test is concerned. Exhaust valve timing controls how much burnt gas is left in the cylinder for the next cycle, so with the phaser locked in one place the engine's hydrocarbon output and lambda value both shift, and both are measured at the fast idle emissions test. On top of that the lamp is a major defect in its own right on petrol cars first used from 1 July 2003 and diesels from 1 July 2008. It is a comparatively cheap fault that fails the car twice, which makes it a sensible one to clear before booking the test.

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

What is camshaft position sensor B?: It is the second camshaft sensor on a bank, which on almost every twin-cam engine reads the exhaust camshaft. Sensor A reads the intake camshaft and is the one the engine uses to work out which stroke each cylinder is on. Sensor B exists because engines with variable timing on both camshafts need to measure both, and it feeds the control of the exhaust phaser. That is why losing sensor B costs you exhaust valve timing control rather than the ability to start.
Can I drive with a P0365 code?: Yes, in the short term. The engine keeps its stroke synchronisation from the other camshaft sensor, so it starts and runs normally in that respect. What you lose is variable control of the exhaust valve timing, which usually parks at a default position, leaving the car feeling flat with a slightly lumpy idle and marginally worse economy. It is not damaging, but it will not repair itself and the lamp will fail an MOT.
What is the difference between P0340 and P0365?: They are the same kind of circuit fault on different sensors of the same bank. P0340 concerns sensor A, normally the intake camshaft, which is the signal the engine uses to synchronise injection and ignition to the four-stroke cycle. P0365 concerns sensor B, normally the exhaust camshaft, which is used to control the exhaust phaser. That is why P0340 typically gives long cranking, stalling and sometimes a no-start, while P0365 usually just gives a flat engine and a poor idle.
Will P0365 fail an MOT?: Yes. The 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, and it fails the car whatever the engine sounds like. There is a second route as well: with the exhaust phaser stuck at its default position the hydrocarbon and lambda readings both shift, and both are measured at the fast idle emissions test.

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