 | |
| Illustration 1 | g02693965 |
Schematic for the Backup Alarm | |
The ECM applies power to the backup alarm whenever the ECM receives a signal from the reverse direction switch.
The possible causes for the backup alarm are listed:
- The backup alarm has failed.
- The harness circuit is open.
- The harness circuit is shorted to ground.
- The ECM has failed.
Note: Ensure that there are no active diagnostic codes for the direction switch.
Test Step 1. CHECK THE BACKUP ALARM
- Disconnect the backup alarm from the harness.
- Use jumpers to connect the respective terminals of the backup alarm to + battery and ground.
Expected Result:
The backup alarm sounds when power is applied.
Results:
- YES - The backup sounds when power is applied. Proceed to Test Step 2.
- NO - The backup alarm does NOT sound. The backup alarm has failed.
Repair: Replace the backup alarm.
STOP
Test Step 2. CHECK FOR A SHORTED HARNESS
The backup alarm remains disconnected.
- Turn the disconnect switch to the OFF position.
- Disconnect the ECM from the harness.
- At the harness connector for the ECM, measure the resistance between contact J1-6 (wire 321-BR) and all ground contacts.
Expected Result:
Each resistance should be greater than 5000 ohms.
Results:
- YES - The resistance is greater than 5000 Ohms (no continuity). The resistance of the harness circuit is correct. Proceed to Test Step 3.
- NO - The resistance is less than 5000 Ohms (continuity). The harness has failed. Wire 321-BR is shorted to ground in the harness.
Repair: Repair the harness or replace the harness.
STOP
Test Step 3. CHECK FOR AN OPEN IN THE HARNESS
The backup alarm and the ECM remain disconnected from the harness.
- The disconnect switch remains OFF.
- At the harness connector for the backup alarm, place a jumper between wire J815-BK and wire 321-BR
- At the harness connector for the ECM, measure the resistance between contact J1-6 (wire 321-BR) to contact J2-8 (wire J815-BK).
Expected Result:
There should be continuity.
Results:
- YES - The resistance is less than 5000 Ohms (continuity). The harness circuit resistance is correct. It is unlikely that the ECM has failed. Perform these Steps again.
Repair: If the cause is not found, replace the ECM. See Testing and Adjusting, "Electronic Control Module (ECM) - Replace".
STOP
- NO - The resistance is greater than 5000 Ohms (no continuity). The harness circuit has failed. Wire J815-BK or wire 321-BR is open in the harness between the ECM and the backup alarm.
Repair: Repair the harness or replace the harness.
STOP