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| Illustration 1 | g01154087 |
Schematic of the backup alarm | |
When the shift lever is in the REVERSE position, a signal is sent to the Power Train/Chassis Electronic Control Module (ECM). The ECM applies power to the backup alarm relay. The ECM switches the relay to ground. When the relay is energized +battery is applied to backup alarm.
If the backup alarm is always off, check these items:
- The backup alarm has failed.
- The machine harness has failed.
- The machine harness is shorted to frame ground.
- The ECM has failed.
- The relay has failed.
Note: Ensure no diagnostic codes are active before performing this procedure.
Test Step 1. CHECK THE POWER SUPPLY TO THE RELAY
- Turn the battery disconnect switch and the key start switch to the ON position.
- Check for +battery at contact 1 (wire 120-YL) of the relay.
Expected Result:
The voltage should be +battery at wire 120-YL.
Results:
- YES - The voltage is +battery at wire 120-YL. The machine harness is correct. Proceed to Test Step 2.
- NO - The voltage is less than +battery.
Repair: Repair machine harness or replace machine harness.
Stop.
Test Step 2. CHECK THE POWER SUPPLY FROM THE RELAY TO THE BACKUP ALARM
- Turn the key start switch and the battery disconnect switch to the OFF position.
- Remove the backup alarm relay.
- At the machine harness connector for the backup alarm relay, place a jumper wire from connector contact 1 (wire 120-YL) to connector contact 4 (wire 612-GY).
- Turn the key start switch and the battery disconnect switch to the ON position.
Expected Result:
The status of the backup alarm is on and the status of the backup alarm is off as the jumper wire is installed and the jumper wire is removed.
Results:
- YES - The backup alarm is on when the jumper wire is installed. Proceed to Test Step 4.
- NO - The backup alarm is off when the jumper wire is installed. Proceed to Test Step 3.
Test Step 3. CHECK THE ALARM CIRCUIT FROM THE RELAY FOR AN OPEN
- Turn the key start switch and the battery disconnect switch to the OFF position.
- Disconnect the machine harness connector from the backup alarm.
- At the machine harness connector for the back up alarm relay measure the resistance from connector contact 4 (wire 612-GY) to connector contact 1 (wire 612-GY) of the backup alarm.
- At the machine harness connector for the backup alarm measure the resistance from connector contact 2 wire 202-BK to frame ground.
Expected Result:
The resistance measured is less than 5 ohms.
Results:
- YES - The resistance measured is less than 5 ohms. The machine harness is correct. Proceed to Test Step 4.
- NO - The resistance measured is greater than 5 ohms. The machine harness for the backup alarm has failed.
Repair: Repair the machine harness or replace the machine harness.
Stop.
Test Step 4. CHECK THE RELAY COIL
- Check the resistance at contact 5 and contact 2 of the relay.
Expected Result:
The resistance should be between 288 ohms to 398 ohms.
Results:
- YES - The resistance is correct. Proceed to Test Step 5.
- NO - The resistance is not within the specified range. The relay has failed.
Repair: Replace the relay.
Stop.
Test Step 5. CHECK THE RELAY CONTACTS
- The battery disconnect switch and the key start switch remain in the OFF position.
- Install the backup alarm relay.
- Reconnect the machine harness connector to the backup alarm relay.
- Turn the battery disconnect switch and the key start switch to the ON position.
- Move the transmission control to the REVERSE position.
- At the machine harness connector for the backup alarm, check for +battery at contact 1 (wire 612-GY) to connector contact 2 (wire 202-BK).
Expected Result:
The voltage should be +battery at wire 612-GY.
Results:
- YES - The voltage is +battery at wire 612-GY. The backup alarm has failed.
Repair: Replace the backup alarm.
Stop.
- NO - The voltage is less than +battery. The relay has failed.
Repair: Replace the relay.
Stop.