PCM Controlled Warning Lamps Diagnosis

Diagnostic Chart:

Wiring Diagram:

Circuit Description

The PCM Controlled lamps are powered through the IGN 1 fuse. The PCM turns ON the bulb, LED, or driver information center indicator by supplying a path the ground through the PCM. Conditions which will illuminate each lamp are as follows:

^ Low Oil Level Lamp: The Low Oil Level Lamp will be illuminated for about a minute when the PCM checks for low oil level and the Engine Oil Level switch indicates that a low oil level condition exists (Engine Oil Level switch circuit not grounded). 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. To test for low oil level at start-up, one of the following conditions must be present:

- If the engine coolant temperature was between 15°C (59°F) and 140°C (284°F) at the last key OFF, the engine coolant temperature at key ON must be at least 12°C (22'F) cooler than the engine coolant temperature at the last key OFF

- If the engine coolant temperature was higher than 140°C (284°F) at the last key OFF, the time between last key OFF and the present key ON must be sufficient to allow the oil to drain back to the sump. The PCM will remain powered up for 15 seconds to ensure that the oil has drained back to the sump. If the key is turned back ON while the PCM is still powered up, the oil level will not be tested.

^ Generator Lamp: The PCM supplies battery voltage to the generator's internal regulator (generator terminal L). When a fault in the Charging System occurs, the internal regulator grounds the L terminal voltage and the PCM commands the generator lamp ON. The PCM will command the generator lamp ON when the following condition(s) are present:

^ Engine speed is above 1200 RPM and system voltage is below 10 volts for at least 10 seconds.

^ The PCM detects a low voltage conditions on the generator's L terminal for at least 10 seconds.

Diagnostic Aids

For diagnosis of the instrument panel, perform the System Check. Refer to Instrument Panel.

Check for the following conditions:

^ Poor connection at PCM or oil level sensor. 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: If the problem was with the Low Oil Level lamp can not be isolated using the PCM Controlled Lamps Diagnostic Table, use the Engine Oil Level Switch Diagnostic Table. Engine Oil Level Sensor/Switch 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 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.