Electronic Control System ISM and QSM11 Engines – 019-168   Maintenance Lamp Circuit

CAUTION  To reduce the possibility of pin and harness damage, use test lead Part Number 3822758.

Turn the vehicle keyswitch to the OFF position. Disconnect the OEM harness connector from the ECM. Disconnect the OEM harness at the main dashboard connector (driver interface panel) beyond the bulkhead connector, in the vehicle cab.

NOTE: Depending on the OEM and the vehicle, the wiring could be run to individual switches instead of a main multi-pin connector. Check the OEM troubleshooting and repair manual for procedures.

Measure the resistance from pin 5 of the OEM harness connector to the back of the lamp.

The multimeter must show a closed circuit
(10 ohms or less).

If the circuit is not closed, repair or replace the OEM harness. Refer to Procedure 019-071.

CAUTION  To reduce the possibility of pin and harness damage, use test lead Part Number 3822758.

Turn the vehicle keyswitch to the OFF position. Disconnect the OEM harness connector from the ECM. Disconnect the OEM harness at the main dashboard connector (driver interface panel), beyond the bulkhead connector, in the vehicle cab.

NOTE: Depending on the OEM and the vehicle, the wiring could be run to individual switches, instead of a main multi-pin connector. Check the OEM troubleshooting and repair manual for procedures.

Measure the resistance from pin 5 of the OEM harness connector to the engine block ground.

The multimeter must show an open circuit
(100k ohms or more). If the circuit is not open, repair or replace the OEM harness. Refer to Procedure 019-071.

Turn the vehicle keyswitch to the ON position.

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

Measure the voltage. The multimeter must
show 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.