P0339 Crankshaft Position Sensor A Circuit Intermittent

P0339 points to an intermittent Crankshaft Position Sensor A circuit. The crank signal is dropping out or becoming unstable only under certain operating conditions.

Code details

Generic OBD-II · P0

System: Ignition / Misfire
Code type: Generic (SAE / ISO controlled)
Standard: SAE J2012 / ISO 15031-6

Diagnostic boundary

A diagnostic trouble code reports that a monitored test failed. It does not prove one specific part is bad, and manufacturer logic can add vehicle-specific conditions.

Do not replace unrelated ignition or fuel parts when the crank signal itself is intermittently disappearing.

Symptoms of P0339

Rough idle, shaking, or a stumble under acceleration.
A flashing check-engine light during an active misfire.
Power loss and higher fuel consumption.

Common causes of P0339

Worn spark plugs, ignition coils, or plug wires.
Fuel-delivery problems — injectors, pressure, or a lean/rich mixture.
Vacuum leaks, low compression, or a mechanical fault in that cylinder.

Useful checks before replacing parts

Review stall history, crank signal status, RPM dropouts, freeze-frame RPM, cam-crank sync, and any no-start or misfire symptoms.
Inspect sensor connector tension, wiring near heat or moving parts, tone wheel condition, sensor mounting, air gap, grounds, and shielding.
Use a scope or scan data recorder during heat, vibration, cranking, and road-load testing to capture the intermittent loss.

Related OBD-II codes

These nearby ignition / misfire entries can help compare wording and pin down the fault area.