Ignition/Distributor Engine Speed Input Circuit Intermittent
Diagnostic Trouble Code P0323 indicates that the Powertrain Control Module (PCM) has detected an intermittent, erratic, or missing signal from the ignition/distributor engine speed input circuit. The PCM relies on this signal to determine engine speed and crankshaft position for proper ignition timing and fuel delivery.
This code is considered high severity because an intermittent engine speed signal can cause the engine to stall unexpectedly while driving or fail to start, 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
- Hesitation or stumbling during acceleration
Likely causes
- Loose, corroded, or damaged wiring and connectors in the engine speed sensor circuit
- Faulty crankshaft position sensor or distributor pickup coil
- Faulty camshaft position sensor (depending on vehicle design)
- Damaged reluctor ring or missing teeth
- Internal distributor failure
- Faulty Powertrain Control Module (PCM) (rare)
What to check before replacing parts
Visually inspect the wiring harness and connectors for the engine speed sensor (crankshaft/camshaft/distributor).
Look for: Look for chafed wires, melted insulation, loose connections, or corrosion in the connector pins that could cause an intermittent signal.
Check the sensor connector for proper voltage and ground using a digital multimeter.
Look for: Verify that the sensor is receiving the correct reference voltage (usually 5V or 12V) and has a solid ground. Intermittent drops in voltage while wiggling the harness indicate a wiring issue.
Test the engine speed sensor's resistance or output signal.
Look for: For a magnetic sensor, check if the resistance is within factory specifications. For a Hall-effect sensor, use an oscilloscope to verify a clean, consistent square wave pattern while cranking or running.
Inspect the reluctor ring (tone ring) on the crankshaft, camshaft, or inside the distributor.
Look for: Check for missing teeth, cracks, excessive debris, or a loose ring that could disrupt the magnetic field and cause an erratic signal.
Check the sensor air gap if it is adjustable.
Look for: Ensure the distance between the sensor tip and the reluctor ring is within the manufacturer's specified tolerance. Too large of a gap can cause a weak or intermittent signal.
This page explains the generic P0323 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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