P0389 Crankshaft Position Sensor B Circuit Intermittent

P0389 indicates an intermittent Crankshaft Position Sensor B circuit. The secondary crank signal drops out, spikes, or becomes unstable only part of the time.

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 call P0389 fixed after a cold idle test if the failure happens hot or only while driving.

Symptoms of P0389

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 P0389

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, hot restart issues, RPM dropouts, crank A versus crank B data, freeze-frame RPM, and cam-crank sync loss.
Inspect connector tension, heat-damaged harness sections, vibration-sensitive wiring, sensor mounting, air gap, shielding, grounds, and tone wheel condition.
Use scope capture or scan data recording while heat-soaking, wiggling the harness, and road-testing to catch the dropout.

Related OBD-II codes

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