P0385 Crankshaft Position Sensor B Circuit Malfunction

P0385 indicates a malfunction in Crankshaft Position Sensor B circuit. The controller is not receiving the expected secondary crankshaft position signal.

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 fuel or ignition parts first when the secondary crank position signal is missing or invalid.

Symptoms of P0385

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 P0385

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

Compare crank sensor B data with crank sensor A, cam sync, RPM while cranking, freeze-frame RPM, and any no-start or stall symptoms.
Inspect sensor power, ground, signal wiring, connector fit, air gap, reluctor or tone wheel condition, shielding, and controller input pins.
Scope the crank B waveform to verify amplitude, pulse spacing, dropout, and synchronization with the primary crank signal.

Related OBD-II codes

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