Possible Causes
NOTE: The listed causes may not be a complete list of all potential issues and there may be other causes.
- Faulty ignition control module
- Ignition control module harness is open or shorted
- Poor electrical connection in ignition control module circuit
Description
The ignition control module (ICM) has independent power and ground circuits.
The circuits between the ICM and powertrain control module (PCM) consist of the following circuits:
– Ignition control (IC) timing signal
– IC timing control
– Low resolution engine speed signal
– Medium resolution engine signal
– Camshaft position signal
– Low reference
The ICM sends 3X signals to the PCM and controls ignition timing during engine starting.
Ignition timing control switches to PCM control after the following actions occur:
The PCM receives the second 3X signal. The PCM applies 5 volts to the ignition control (IC) timing signal circuit.
The ICM monitors the CKP timing signal when the engine starts. The CKP timing signal is transmitted from the CKP sensor to the ICM on the CKP sensor signal 2 circuit.
The CKP timing signal is used to determine the correct cylinder pair and initiate the ignition coil firing sequence.
The 18X reference pulses are transmitted from the CKP sensor to the ICM on the CKP sensor 1 circuit.
The 18X reference pulses are used for fuel injection and ignition control.
Once the ICM has received both signals, it transmits the 18X and 3X reference signals to the PCM.
The CMP and CKP sensors share a 12-volt reference circuit and a low reference circuit.
The CKP sensor consists of the following circuits:
– A 12-volt reference
– A low reference
– A CKP sensor signal 1
– A CKP sensor signal 2
How to Repair
Check the “Possible Causes” listed above. Visually inspect the related wiring harness and connectors. Check for damaged components and look for broken, bent, pushed out, or corroded connector pins.
Possible Symptoms
- MIL illuminated (or service engine soon warning light)