Ignition/Distributor Engine Speed Input Circuit Range/Performance
The PCM has detected a problem with the ignition/distributor engine speed sensor circuit, which measures crankshaft position and RPM. Without a valid signal from this sensor, the engine cannot fire spark plugs at the correct time, preventing proper ignition timing and engine operation.
What You Might Notice
- Check Engine Light (MIL) illuminated
- Engine cranks but will not start
- Engine misfires, hesitates, or stumbles
- Lack of engine power and poor acceleration
- Stalling or rough idle
Most Common Causes
- 1
Faulty crankshaft position sensor
The sensor itself has failed electrically or mechanically, causing it to send incorrect or no signal to the PCM about engine speed and ignition timing.
- 2
Open circuit in wiring harness
A break or loose connection in the sensor's power supply, ground, or signal wires prevents proper communication between the sensor and PCM.
- 3
Short to ground in sensor circuit
Damaged insulation or a direct short in the power supply wiring to the sensor causes the circuit to fail and prevents normal sensor operation.
- 4
PCM failure or defect
The powertrain control module itself has failed or cannot properly read the sensor input signal, though this is less common than sensor or wiring issues.
How to Diagnose It
- 1
Check Faulty crankshaft position sensor — The sensor itself has failed electrically or mechanically, causing it to send incorrect or no signal to the PCM about engine speed and ignition timing.
- 2
Check Open circuit in wiring harness — A break or loose connection in the sensor's power supply, ground, or signal wires prevents proper communication between the sensor and PCM.
- 3
Check Short to ground in sensor circuit — Damaged insulation or a direct short in the power supply wiring to the sensor causes the circuit to fail and prevents normal sensor operation.
- 4
Check PCM failure or defect — The powertrain control module itself has failed or cannot properly read the sensor input signal, though this is less common than sensor or wiring issues.
How to Fix It
- 1
Test and replace crankshaft position sensor
Use a multimeter to test sensor resistance and output voltage; if readings are out of spec or absent, replace the sensor with an OEM or quality aftermarket unit.
- 2
Inspect and repair sensor wiring and connectors
Visually inspect the sensor harness for damage, corrosion, or loose connections; repair or replace any damaged wires and clean corroded connectors with contact cleaner.
- 3
Check sensor power and ground circuits
Using a multimeter, verify that the sensor receives proper voltage (typically 5V or 12V depending on vehicle) and has a solid ground connection; repair any broken grounds or power supply wires.
- 4
Test or replace PCM if sensor and wiring are good
If the sensor, wiring, and connectors test good but the code persists, the PCM may have failed and require replacement or reprogramming by a qualified technician.
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