What it means
The crankshaft position sensor A signal jumps or drops out intermittently — connector, sensor air gap, or damaged tone wheel. The PCM may detect a "false" stall or misfire spike when the signal drops.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
Crankshaft position sensor A reports crankshaft rotation to the controller, which uses the signal to maintain ignition and fuel timing. P0339 sets when that signal intermittently drops out or changes unexpectedly, potentially causing a false stall indication, hesitation, or an abrupt engine stop.
Common causes
Most likely first.
- Intermittent connector
- Tone wheel chipped or contaminated
- Connector with intermittent contact under vibration
Symptoms
- Check-engine light
- Intermittent stalling
- Hesitation or rough running
- Erratic tachometer reading
How to diagnose it
- Review freeze-frame data and scan live engine-speed readings for sudden dropouts, and note whether they occur over bumps, when hot, or during acceleration.
- Inspect sensor A's connector and harness for loose terminals, corrosion, chafing, or damage that could interrupt contact during vibration.
- Check the tone wheel or reluctor for chipped teeth, contamination, or other visible damage where accessible.
- Monitor the crank signal while checking the harness and connector for intermittent contact using the manufacturer's procedure.
- Test sensor A and verify its mounting and air gap against the manufacturer's specification, then repair the cause of the signal dropout.
Common fixes
- Secure the sensor A connector or repair an intermittent connection in its wiring.
- Repair chafed or heat-damaged wiring in the crankshaft sensor A circuit.
- Clean an accessible contaminated tone wheel or repair a damaged reluctor as specified.
- Correct sensor mounting or air gap, or replace sensor A if it fails the specified test.
Can I keep driving?
Intermittent signal loss can stall the engine without warning, so avoid busy roads, long trips, and situations where a sudden stop would be dangerous. If stalling or repeated hesitation occurs, stop driving until the cause is repaired.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.