PCM Controlled Warning Lamps Diagnosis

Diagnostic Chart:

Diagnostic Chart (cont'd):

Wiring Diagram:

CIRCUIT DESCRIPTION

The PCM controlled lamps are powered through an ignition feed fuse. The PCM commands the instrument panel cluster to turn ON the Check Gauges indicator by grounding the generator status circuit.


DIAGNOSTIC AIDS

A PCM controlled lamp ON at all times most likely indicates that a condition is present which requires the attention of the vehicle operator.

Low Oil Level Lamp will be illuminated for about a minute after the ignition has been turned ON when the PCM tests for low oil level and the engine oil level sensor indicates that a low oil level condition exists. The PCM determines whether or not to test for low oil level based on the difference between engine coolant temperature at the last shutdown and engine coolant temperature at start-up. This is to ensure that the oil has drained back into the sump before testing. When the ignition is first turned ON, the PCM commands the Low Oil Level lamp ON for a brief period of time to test the bulb.

Check for the following conditions:

- Poor connection at PCM. Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection.

- Damaged harness. Inspect the wiring harness for damage. If the harness appears to be OK, disconnect the PCM and turn the ignition ON. Observe a voltmeter connected to the affected PCM output circuit while moving connectors and wiring harnesses related to the PCM output circuit. A change in voltage will indicate the location of the fault.

- Engine oil level sensor circuit: Use the Engine Oil Level Sensor Diagnosis.


TEST DESCRIPTION

Number(s) below refer to the step number(s) on the Diagnostic Chart.

3. Normally, ignition feed voltage should be present on the output control circuit with the PCM disconnected and the ignition turned ON.

4. Checks for a shorted component or a short to B+ on the output control circuit. Either condition would result in a measured current of over 1.5 amps. Also checks for a component that is going open while being operated, resulting in a measured current of 0 amps.

5. Checks for a faulty instrument cluster.

16. This vehicle is equipped with a PCM which utilizes an Electrically Erasable Programmable Read Only Memory (EEPROM). When the PCM is being replaced, the new PCM must be programmed.