The ECM applies power to the backup alarm whenever the ECM receives a signal from the reverse direction switch.
- The backup alarm has failed.
- The harness circuit is shorted to ground. (alarm is always ON)
- The harness circuit is open. (alarm does not sound)
- The ECM has failed.
Note: Ensure that there are no active diagnostic codes for the direction switch.
Check the backup alarm.
- Disconnect the backup alarm from the harness.
- Use jumpers to connect the respective terminals of the backup alarm to a + battery and ground.
Expected Result:
The backup alarm sounds when power is applied.
Result:
YES: The backup alarm sounds when power is applied. Proceed to "The Harness Circuit Is Shorted To Ground.".
NO: The backup alarm does NOT sound. The backup alarm has failed.
Repair: Replace the backup alarm.
STOP.
The Harness Circuit Is Shorted To Ground.
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 J2-6 (wire 321-BR(Brown)) and all possible sources of ground.
Expected Result:
Each resistance should be greater than 5 KΩ.
Result:
YES: The resistance is greater than 5 KΩ (no continuity). The resistance of the harness circuit is correct. Proceed to "The Harness Circuit Is Open. (Alarm Does Not Sound)".
NO:The resistance is less than 5 KΩ (continuity). The harness has failed. Wire (321-BR(Brown)) is shorted to ground in the harness.
Repair: Repair the harness or replace the harness.
STOP.
The Harness Circuit Is Open. (Alarm Does Not Sound)
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 ECM, place a jumper from contact J2-6 (wire 321-BR(Brown)) to ground.
- At the harness for the backup alarm, measure the resistance from wire 321-BR(Brown) to ground.
- At the alarm connector, measure the resistance to ground on circuit H807.
Expected Result:
There should be continuity.
Result:
YES: The resistance is less than 5 Ω (continuity). The harness circuit resistance is correct. ECM failure is unlikely. Perform these Steps again.
If the cause is not found, replace the ECM. Refer to Troubleshooting, "ECM - Replace" in this manual.
NO: The resistance is greater than 5 K Ω (no continuity). The harness circuit has failed. Wire (321-BR(Brown)) is open in the harness between the ECM and the backup alarm relay.
Repair: Repair the harness or replace the harness.
STOP.