Electronic Ignition (EI) System Diagnosis

Circuit Description
A Crankshaft Position (CKP) sensor determines the engine crankshaft position. The sensor is mounted and protrudes into the right side of the engine block. The sensor is near a slotted wheel on the crankshaft. The rotation of the slotted wheel causes a magnetic flux change in the sensor. This produces a voltage signal from the electronic Ignition Control Module (ICM). The signal creates the reference pulses needed by the Powertrain Control Module (PCM). These signals trigger the correct ignition coil to fire, at the correct time.

The ignition system on this engine uses an individual ignition coil/module for each cylinder. The PCM controls the ignition system operation. There are eight Ignition Control (IC) circuits, one per cylinder, that connect the PCM and the ignition coil/modules. Each ignition coil/module has a power feed, a chassis ground circuit, and a reference low circuit. The PCM causes a spark to occur by grounding the IC circuit, which signals the ignition module to trigger the ignition coil and fire the spark plug. The PCM controls the sequencing and timing.

Diagnostic Aids

Important: Remove any debris from the PCM connector surfaces before servicing the PCM. Inspect the PCM connector gaskets when diagnosing/replacing the PCM. Ensure that the gaskets are installed correctly. The gaskets prevent water intrusion into the PCM.

The following may cause an intermittent:
^ Check for poor connections. Check for adequate terminal tension. Refer to Intermittents and Poor Connections Diagnosis.
^ Corrosion
^ Mis-routed harness
^ Rubbed through wire insulation
^ Broken wire inside the insulation
For an intermittent condition, refer to Symptoms. Intermittent Conditions

Test Description
The numbers below refer to the step numbers on the diagnostic table.
3. Monitoring the misfire current counters determines if a fault is present.
4. A good indication that the fuse is open is all the misfire current counters are incrementing on one side of the engine. Inspect the ignition feed circuit for a grounded circuit.
8. If the fuse is open and the ignition coil/module circuits are OK, inspect the injector circuits for being grounded. The INJ A fuse and INJ B fuse feed the ignition coil/module circuits and injector circuits.