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| Illustration 1 | g01340899 |
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). Circuit Breaker 6 supplies power to the backup alarm relay. Circuit Breaker 13 supplies power to the backup alarm relay coil. The Power Train/Chassis ECM switches the relay to frame ground. When the backup alarm relay is energized, +battery is applied to backup alarm.
If the backup alarm is always on, check these items:
- The harness is shorted to +battery.
- The harness is shorted to ground.
- The backup alarm relay has failed.
- The Power Train/Chassis ECM has failed.
Test Step 1. CHECK THE RELAY
- Turn the key start switch and the battery disconnect switch to the OFF position.
- Remove the backup alarm relay.
- Turn the battery disconnect switch and the key start switch to the ON position.
Expected Result:
The backup alarm is off.
Results:
- YES - The backup alarm is off. Proceed to Test Step 2.
- NO - The backup alarm is on. Proceed to Test Step 4.
Test Step 2. CHECK THE RELAY CONTACTS
- Turn the key start switch and the battery disconnect switch to the OFF position.
- The backup alarm relay remains removed.
- Check the resistance between contact 1 and contact 4 of the backup alarm relay.
Expected Result:
The resistance should be greater than 5 ohms.
Results:
- YES - The resistance is greater than 5 ohms. Proceed to Test Step 3.
- NO - The resistance is less than 5 ohms. The backup alarm relay has failed.
Repair: Replace the backup alarm relay.
STOP
Test Step 3. CHECK THE RETURN CIRCUIT OF THE BACKUP ALARM RELAY FOR A SHORT TO GROUND
- At the connector of the backup alarm relay measure the resistance between contact 2 (wire 331-OR) J2-12 and frame ground.
Expected Result:
The resistance should be greater than 5 ohms.
Results:
- YES - The resistance is greater than 5 ohms. Proceed to Test Step 4.
- NO - The resistance is less than 5 ohms. The machine harness has failed.
Repair: Repair the machine harness or replace the machine harness.
STOP
Test Step 4. CHECK THE SIGNAL CIRCUIT OF THE BACKUP ALARM FOR A SHORT TO +BATTERY
- Turn the key start switch and the battery disconnect switch to the OFF position.
- Disconnect the machine harness from the backup alarm.
- At the connector of the backup alarm relay measure the resistance between contacts 1 (wire 120-YL) and contacts 4 (wire 612-GY), and between contacts 4 (wire 612-GY and contacts 5 (wire 126-PK) of the connector.
Expected Result:
Each resistance should be greater than 5 ohms.
Results:
- YES - The resistance is greater than 5 ohms. Proceed to Test Step 5
- NO - The resistance is less than 5 ohms. The machine harness has failed.
Repair: Repair the machine harness or replace the machine harness.
STOP
Test Step 5. CHECK IF THE PROBLEM REMAINS
- Inspect the contacts of the harness connectors and clean the harness connectors.
- Reconnect all the harness connectors.
- Operate the machine.
- Check to see if the fault still occurs.
Expected Result:
The fault is present.
Results:
- YES - The fault is present. The fault has not been corrected. The Power Train/Chassis ECM may have failed.
Repair: It is unlikely that the Power Train/Chassis ECM has failed. Exit this procedure and perform this procedure again. If the cause of the fault is not found, replace the Power Train/Chassis ECM. Refer to Systems Operation, Troubleshooting, Testing and Adjusting,, "Electronic Control Module ECM - Replace".
STOP
- NO - The fault is no longer present. The fault does not exist at this time.
Repair: The initial fault was probably caused by a poor electrical connection or a short at one of the harness connectors that was disconnected and reconnected. Resume normal machine operation.
STOP