Electronic Control System ISM and QSM11 Engines – 019-167   Maintenance Lamp

The engine protection system uses a lamp or a buzzer to alert the driver of one of the following conditions:

1. Low coolant level
2. High coolant temperature
3. Low oil pressure
4. High oil pressure
5. High intake manifold temperature
6. Very low oil pressure.

The maintenance lamp circuit is a positive (+) 12-VDC (24 VDC in the United Kingdom or Europe) supply from the vehicle keyswitch, a lamp or buzzer, and wire No. 5.

The ECM provides a ground path for the circuit to illuminate the lamp.

Turn the vehicle keyswitch to the ON position.

Touch the positive (+) multimeter probe to the buzzer or lamp terminal. Touch the negative (-) multimeter probe to the chassis ground.

Measure the voltage. The multimeter mustshow battery voltage. If the proper voltage is not present, there is a problem with the keyswitch wire or the lamp (or buzzer) has failed. Refer to the OEM troubleshooting and repair manual for repair procedures.

Repeat this check for the other terminal of the buzzer or fault lamp. The multimeter mustshow the battery voltage.

If battery voltage is notpresent, there is a problem with the keyswitch line or the lamp has failed. Refer to the OEM troubleshooting and repair manual for procedures.

NOTE: The battery voltage will vary between vehicles, depending on the age and the condition of the batteries. There mustbe enough voltage available to illuminate the lamp.

Touch the positive (+) multimeter probe to the other fault lamp terminal.

Touch the negative (-) multimeter probe to chassis ground.

Measure the voltage. The multimeter mustshow battery voltage. If the proper voltage is notpresent, there is a problem with the keyswitch wire or the lamp (or buzzer) has failed. Refer to the OEM troubleshooting and repair manual for repair procedures.

Repeat this check for the other terminal of the fault lamp. The multimeter mustshow battery voltage. If battery voltage is notpresent, there is a problem with the keyswitch line or the lamp has failed. Refer to the OEM troubleshooting and repair manual for procedures.

Repeat this test for the other terminal of the buzzer or fault lamp.

Connect all components after the repair is complete.