Crankshaft Position Sensor "A" Circuit

What it means

The crankshaft position (CKP) sensor reads a toothed reluctor or trigger wheel on the crankshaft and supplies the ECU with engine speed and the reference point for ignition and injection timing. P0335 sets when the ECU receives no CKP signal, an implausible number of pulses per revolution, or signal dropouts while the engine is cranking or running, often confirmed by the camshaft sensor showing rotation while the crank signal is missing. Without a valid crank signal the ECU cannot fire the coils or injectors, so the engine stalls or will not start.

Symptoms

• Engine cranks but will not start, or starts only after extended cranking
• Sudden stalling while driving, often when the engine is hot, restarting after it cools
• Intermittent cut-outs or jerking at speed
• Tachometer reads zero or drops out while the engine is running
• Check engine light and rough running or misfire codes when the signal is noisy

Common causes

1. Failed crankshaft position sensor, often heat-related and intermittent before total failure
2. Damaged, chafed or oil-soaked wiring, or a corroded connector between the sensor and ECU
3. Cracked, missing teeth or loose reluctor/trigger wheel on the crankshaft or flywheel
4. Metal debris stuck to a magnetic sensor tip or excessive air gap after a repair
5. Loss of 5 V or 12 V supply or ground to a Hall-type sensor
6. Electrical interference from a failing ignition coil or alternator inducing noise on the signal wire
7. ECU input circuit fault (rare)

How to diagnose

1. Confirm the complaint on the scan tool: during cranking the rpm PID should show about 150–300 rpm; a reading of 0 rpm while the engine is turning indicates no crank signal reaching the ECU
2. Inspect the sensor wiring and connector for oil contamination from a leaking front seal, chafing against brackets, and corroded or pushed-back terminals; wiggle the harness with the engine running and watch for stalling
3. Identify the sensor type: a 2-wire inductive sensor should read roughly 200–1,500 ohms and produce an AC voltage of 0.5–1 V or more while cranking; a 3-wire Hall sensor needs 5 V or 12 V supply, a good ground and produces a square wave switching between near 0 V and the supply voltage
4. Scope the signal while cranking and at idle: look for a clean, even pattern with a clear missing-tooth gap once per revolution; irregular or missing pulses point to a damaged reluctor wheel or sensor
5. Check the air gap and mounting: the sensor must be fully seated with the correct bolt torque, and on magnetic sensors the tip must be free of swarf; inspect the reluctor wheel for cracks or a shifted key
6. Heat-soak test for intermittent failures: warm the sensor gently with a heat gun while monitoring the signal; signal loss above about 90–100 °C confirms a thermally failing sensor

Symptoms linked to this code

• Engine cranks but won't start
• Car stalls at idle

Terms to know

Related codes

Nearby codes in this group

• P0334Knock Sensor 2 Circuit Input Intermittent
• P0336Crankshaft Position Sensor A Circuit Range/Performance
• P0333Knock Sensor 2 Circuit High Input (Bank 2)
• P0337Crankshaft Position Sensor A Circuit Low Input
• P0332Knock Sensor 2 Circuit Low Input (Bank 2)
• P0338Crankshaft Position Sensor A Circuit High Input
• P0331Knock Sensor 2 Circuit Range/Performance
• P0339Crankshaft Position Sensor A Circuit Intermittent