Sensors and circuits

P0335Crankshaft position sensor A circuit

Crankshaft Position Sensor A Circuit

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Generic OBD-II code

Crankshaft Position (CKP) Sensor

What this part does

Reports crankshaft position and engine speed, the primary timing reference the control module uses for fuel and spark synchronization.

What the computer is measuring

The crankshaft position sensor is the single most important input the engine has. It tells the computer where the crankshaft is and how fast it is turning, and everything the engine does is timed from it. Injection timing, ignition timing and the misfire monitor all start from this signal. Without it the computer cannot know when to fire anything, so it does not try. That is why a failed crankshaft sensor gives a car that cranks perfectly and never catches.

The sensor reads a toothed ring on the crankshaft, usually with one or two teeth deliberately missing. Those gaps are how the computer works out absolute position rather than just speed. Each tooth passing produces a pulse, the gap produces a recognisable break in the pattern, and from that the computer knows exactly where in the rotation it is.

P0335 means that pattern was missing, unreadable or implausible. The circuit in the code name covers the sensor, its wiring and the reference the sensor reads, so a good sensor with a damaged ring sets the same code as a dead one.

Why this code is so often intermittent

The failure mode most people meet is not a sensor that has stopped. It is a sensor that stops when it gets hot. The windings inside develop a break that opens as the material expands, so the car starts and runs from cold, then cuts out after twenty minutes of driving and refuses to restart until it has cooled down.

If that description matches, do not be reassured by a sensor that tests fine on a cold engine. The test that means something is the one carried out while the fault is present.

Do not assume a no start is this code

Cranking without starting has several causes, and the useful thing about this one is that it can be confirmed rather than guessed. If engine speed reads zero on a scan tool while the engine is cranking, the computer genuinely is not seeing the crankshaft. If it reads a normal cranking speed, the timing reference is arriving and the reason it will not start is somewhere else entirely.

What you will notice

  • Cranking with no start, sometimes after the engine has been running perfectly a minute earlier.
  • Stalling without warning, then restarting after it has stood for twenty minutes.
  • The rev counter dropping to zero or flickering while the engine is cranking or running.
  • Long cranking before it catches, and hesitation or a sudden cut out under load.

Likely causes, most common first

Ordered by how often each one actually turns out to be the problem, not alphabetically and not by part price.

  1. A failed crankshaft position sensor

    The most common cause, and it usually fails with heat. Fine cold, dead once the engine bay is hot, which is exactly the pattern of a car that will not restart after a long run.

  2. Damaged wiring or a corroded connector

    The sensor sits low on the block near the bellhousing, where oil, heat and road spray all reach it. Chafed insulation and green pins are common.

  3. Debris or damage on the reluctor ring

    The toothed ring the sensor reads. A missing tooth, a build up of metal debris or a ring that has shifted produces an unreadable pattern from a perfectly good sensor.

  4. A loose sensor or an incorrect air gap

    Usually appears shortly after other work in that area. The sensor has to sit at a set distance from the ring to produce a usable signal.

  5. A crankshaft variation relearn that was never carried out

    Some vehicles need a relearn procedure after a sensor, an engine or a module is replaced, and will store this code until it is done. Frustrating, free to fix, and easily mistaken for a faulty new part.

  6. Electrical interference or a failing alternator

    Less common, but a noisy charging system or badly routed aftermarket wiring can corrupt a low level signal running alongside it.

What to check, in order

  1. Watch engine speed in live data while someone cranks the engine.

    Zero rpm while cranking confirms no usable signal is reaching the computer. An rpm figure that appears normally means the signal exists and the fault is intermittent, so it has to be caught while it is happening.

  2. Inspect the connector and the wiring back from the sensor.

    Oil in the connector, chafed insulation or corroded pins explain the code without replacing the sensor. Clean, sound wiring moves the fault to the sensor or the ring.

  3. Measure the sensor. An inductive type has a coil with a resistance value to check, and a hall type has a supply, a ground and a signal to confirm.

    An open or badly out of specification coil confirms a failed inductive sensor. Correct resistance, or correct supply and ground on a hall type, clears the sensor electrically.

  4. Look at the reluctor ring through the sensor mounting hole while the engine is turned over by hand.

    Missing or damaged teeth, or debris bridging them, is the fault and no sensor will fix it.

  5. If the fault only appears hot, get the engine up to temperature and repeat the live data check while it is failing.

    A signal that disappears only when hot is the classic failed sensor pattern and is worth confirming rather than assuming, because wiring near the exhaust behaves the same way.

Where this one turns up most

  • Vehicles over about a hundred thousand miles, where heat cycling has finally reached the sensor windings.
  • Engines where the sensor sits low at the rear of the block and is exposed to oil leaks from above.

Codes that often show up alongside it

What a DriveDecode adapter can read

A DriveDecode adapter reads engine and emissions systems: the powertrain and emissions codes the OBD-II standard requires on every US vehicle it covers. It does not read ABS, airbag (SRS), TPMS or transmission-specific manufacturer codes. Those need make-specific decoding that generic OBD-II hardware cannot do.

Reading P0335 on your own car

DriveDecode pulls P0335 straight off the vehicle along with the freeze frame the computer stored when it set: the coolant temperature, engine load and speed at that exact moment. That context is what separates a fault that happens on a cold start from one that happens under load, and it is the first thing the list above asks you to narrow down.

See how DriveDecode works

Last reviewed 2026-09-08. Definition sourced from the published standard.