Ignition/Distributor Engine Speed Input Circuit
Diagnostic Trouble Code P0320 indicates a malfunction in the ignition/distributor engine speed input circuit. The Powertrain Control Module (PCM) sets this code when it fails to receive a consistent or valid engine speed signal from the ignition system, crankshaft position sensor, or camshaft position sensor.
This code is considered high severity because the loss of the engine speed signal can cause the engine to stall unexpectedly while driving or prevent the vehicle from starting, posing a significant safety risk.
Common symptoms
- Illuminated Check Engine Light
- Engine stalling or dying unexpectedly
- Engine cranks but will not start
- Rough idling or engine misfires
- Tachometer drops to zero or behaves erratically
Likely causes
- Faulty crankshaft position sensor
- Faulty camshaft position sensor
- Damaged, corroded, or loose wiring and connectors in the engine speed input circuit
- Faulty ignition control module
- Defective distributor pickup coil (on older distributor-equipped vehicles)
- Failing Powertrain Control Module (PCM) (rare)
What to check before replacing parts
Visually inspect the wiring and connectors for the crankshaft and camshaft position sensors.
Look for: Look for frayed wires, melted insulation, loose connections, or corrosion that could interrupt the signal to the PCM.
Check the battery voltage and ground connections.
Look for: Ensure the battery is fully charged and that engine grounds are clean and tight, as low voltage can cause erratic sensor signals.
Test the crankshaft position sensor using a digital multimeter or oscilloscope.
Look for: Check for proper resistance according to service manual specifications, or verify a clean, consistent square wave or AC voltage signal while cranking.
Test the camshaft position sensor or distributor pickup coil.
Look for: Verify the sensor is producing the correct voltage signal or resistance as specified by the manufacturer, with no dropouts during operation.
Check the wiring harness for continuity and shorts between the sensors and the PCM.
Look for: Use a multimeter to ensure there is very low resistance (continuity) on the signal wires and no short to ground or power.
This page explains the generic P0320 definition and is general reference information, not a diagnosis for your specific vehicle. Actual causes, severity, and repairs vary by make, model, engine, and mileage — always confirm with a scan tool and a qualified technician before replacing parts.
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