Will a bad crank sensor always set a code?

No. A signal that disappears abruptly can stop the engine before the computer records a clean failure. Hot-stall history, RPM data while cranking, and signal testing matter.

How can I tell the sensor from its wiring?

Inspect the harness near hot or moving parts, confirm connector pin tension, and test power/ground and signal at the connector. A new sensor cannot repair a missing supply, bad ground or broken signal wire.

Can I drive with an intermittent crank sensor?

It is risky because the engine can stop without warning and may not restart until it cools. Diagnose it promptly rather than waiting for a permanent no-start.

Why did the new sensor not fix the code?

Common reasons are damaged wiring, incorrect air gap, metal debris, a damaged reluctor wheel, a low-quality replacement sensor, or a cam/crank timing problem rather than the sensor itself.

Crankshaft Position Sensor: Symptoms and Testing

Also known as: CKP sensor · crank sensor · engine speed sensor

Quick answer

The crankshaft position sensor tells the engine computer crank speed and exact piston position so it can time spark and injection. Failure can cause cranking with no start, sudden stalling, tachometer drop-out, misfires, or P0335–P0339. Inspect its connector and wiring, then test signal quality before replacing the sensor.

The crankshaft position sensor reads teeth or windows on a reluctor wheel as the crank rotates. That signal is the engine computer’s timing reference; without a believable crank signal, many systems will withhold spark and injector pulse.

Some sensors fail with heat and work again after cooling. Others are healthy but report a weak signal because the connector is corroded, wiring is rubbed through, the air gap is wrong, or the reluctor wheel is damaged.

A scan tool showing zero RPM while the engine is cranking is a useful clue, not a complete conviction. Verify power, ground and signal based on the sensor design; an oscilloscope gives the clearest answer on intermittent faults.

Signs it’s failing

⚠ Engine cranks normally but will not start
⚠ Sudden stall, often after the engine warms up
⚠ Tachometer drops instantly to zero during the failure
⚠ Intermittent extended cranking
⚠ Misfire, rough running, or reduced-power mode
⚠ P0335, P0336, P0337, P0338 or P0339

Trouble codes this part can trigger

Frequently asked questions

Will a bad crank sensor always set a code?: No. A signal that disappears abruptly can stop the engine before the computer records a clean failure. Hot-stall history, RPM data while cranking, and signal testing matter.
How can I tell the sensor from its wiring?: Inspect the harness near hot or moving parts, confirm connector pin tension, and test power/ground and signal at the connector. A new sensor cannot repair a missing supply, bad ground or broken signal wire.
Can I drive with an intermittent crank sensor?: It is risky because the engine can stop without warning and may not restart until it cools. Diagnose it promptly rather than waiting for a permanent no-start.
Why did the new sensor not fix the code?: Common reasons are damaged wiring, incorrect air gap, metal debris, a damaged reluctor wheel, a low-quality replacement sensor, or a cam/crank timing problem rather than the sensor itself.