Electronic Control System Signature, ISX and QSX15 Engines – 019-168   Maintenance Lamp Circuit

CAUTION  To avoid pin and harness damage, use test lead Part No. 3822758.

Turn the 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, the wiring could be run to individual switches instead of a main multi-pin connector. Refer to the OEM troubleshooting and repair manual for the wiring configuration of your vehicle.

Insert a test lead into pin 5 of the OEM harness connector and connect it to a multimeter probe. With the other multimeter probe, touch the back of the lamp. Measure the resistance. 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. Connect all components after completing the repair.

CAUTION  To avoid pin and harness damage, use test lead Part No. 3822758.

Turn the 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, the wiring could be run to individual switches, instead of a main multi-pin connector. Refer to the OEM troubleshooting and repair manual for the wiring configuration of your vehicle.

Insert a test lead into pin 5 of the OEM harness connector and connect it to a multimeter probe. Touch the other multimeter probe to the engine block ground. Measure the resistance.

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. Connect all components after completing the repair.

Turn the 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. Connect all components after completing the repair.