P0320 Ignition/Distributor Engine Speed Input Circuit Malfunction

P0320 indicates a malfunction in the ignition or distributor engine speed input circuit. The controller is not receiving the engine speed information it expects from the ignition, distributor, or related speed signal path.

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 the PCM for P0320 until the engine speed signal path, wiring, and waveform have been tested under the failure condition.

Symptoms of P0320

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 P0320

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

Check RPM signal behavior while cranking and running, crankshaft sensor data, distributor pickup data where used, ignition reference signal, and freeze-frame RPM.
Inspect sensor power, ground, signal wiring, connector fit, shielding, reluctor or tone wheel condition, ignition module wiring, and PCM input pins.
Use a scope when possible to confirm waveform shape, amplitude, dropouts, and interference before condemning the sensor or controller.

Related OBD-II codes

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