Component Tests and General Diagnostics

CIRCUIT DESCRIPTION
The ignition control module (ICM) has independent power and ground circuits. The circuits between the ICM and the powertrain control module (PCM) consists of the following circuits:
^ The ignition control (IC) timing signal
^ The IC timing control
^ The low resolution engine speed signal
^ The medium resolution engine signal
^ The camshaft position signal
^ The low reference

Both the camshaft position (CMP) sensor and crankshaft position (CKP) sensor signals are input directly to the ICM. The ICM sends 3X signals to the PCM, and controls the timing advance during engine cranking. The timing advance changes 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.

DIAGNOSTIC AIDS
If the CMP signal is not present at start-up, the PCM will begin sequential fuel delivery with a 1 in 6 chance that fuel delivery is correct.

An intermittent may be caused by a poor connection, rubbed through wire insulation or a wire broken inside the insulation. Inspect for the following items:
^ Poor connection or damaged harness-Inspect the PCM harness and connectors for improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wire connection, and damaged harness.
^ Faulty engine coolant temperature (ECT) sensor- Using a scan tool, compare ECT with intake air temperature (IAT) on a completely cool engine. ECT should be within 10°C of IAT. If not, replace the ECT sensor. Refer to Engine Coolant Temperature (ECT) Sensor Replacement.

TEST DESCRIPTION

Steps 1-9:

Steps 10-17:

Steps 18-24:

Steps 25-33:

The numbers below refer to the step numbers on the diagnostic table.
3. This step determines if the ignition control module (ICM) is receiving the CKP sensor 1 signal. If the CKP sensor 1 signal to the ICM is not present, there will be no RPM, spark, or fuel injector pulses.
4. This step ensures that the ICM has the proper voltage supply and ground.
6. This step verifies that the ICM is supplying the 10 volt reference to the sensor.
15. Inspect for the proper operation of the CKP sensor 2 signal, ICM and related spark system components. Without the CKP sensor 2 signal the ICM is unable to properly sequence the ignition coils.
26. If the CKP sensor 1 signal and CKP sensor 2 signals to the PCM or the medium resolution and low resolution engine speed signals to the ICM short together the vehicle will not start and run. However, there will be spark and fuel injector pulses.