PCM Controlled Warning Lamps Diagnosis

Circuit:

CIRCUIT DESCRIPTION

The PCM controlled lamps are powered through the IGN 1 fuse. The PCM turns ON the bulb, LED, or driver info center indicator by supplying a path to ground through the PCM.


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. Conditions which will illuminate each lamp are as follows:

^ GENERATOR LAMP will be illuminated under any of the following conditions:

- When the engine speed is greater than 1200 RPM and system voltage falls below 9 volts for longer than 25 seconds. The PCM commands the generator lamp OFF when system voltage rises to above 12 volts.

- When the generator control circuit (L terminal) remains low for longer than 25 seconds.

For diagnosis of the instrument panel, perform the System Check in the Instrument Cluster section.

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.


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 driver circuit with the PCM disconnected and the ignition turned ON.

4. Checks for a shorted component or a short to B+ on the output driver 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. Refer to PCM Replacement/Programming.