Possible Causes
NOTE: This list is not exhaustive and other issues may be causing the situation.
- Faulty ignition control module (ICM)
- Open or shorted ICM wiring harness
- Faulty electrical connection in the ICM circuit
Description
The ignition control module (ICM) has independent power and ground circuits. The connections between the ICM and the powertrain control module (PCM) include:
- The ignition control (IC) synchronization signal
- The IC synchronization control
- Low and medium resolution engine speed signals
- Camshaft position signal
- A low reference
The ICM transmits 3X signals to the PCM and manages timing advance during engine startup. Once the following steps are completed, timing advance management switches to the PCM:
- The PCM receives a second 3X signal.
- The PCM applies a 5-volt voltage to the IC synchronization signal circuit.
During startup, the ICM monitors the CKP synchronization signal sent by the CKP sensor via the corresponding circuit. This signal is used to identify the correct cylinder pair and trigger ignition.
The CKP sensor also sends 18X reference pulses to the ICM. These pulses are essential for fuel injection and ignition control. Once both signals are received, the ICM transmits them as 18X and 3X references to the PCM.
The CMP (camshaft) and CKP (crankshaft) sensors share:
- A 12-volt power supply
- A low reference
The CKP sensor circuits include:
- A 12-volt power supply
- A low reference
- A CKP 1 signal
- A CKP 2 signal
How to Repair
- Check the possible causes mentioned above.
- Visually inspect the wiring harness and associated connectors.
- Look for damaged components, as well as broken, bent, displaced, or corroded connector pins.
Diagnostic
The PCM detects a break in the ignition control module (ICM).
Possible Symptoms
- Engine light on (or maintenance required light).