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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 on, check these items.
- The harness is shorted to +battery.
- The ECM has failed.
- The relay 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 back up 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
- The backup alarm relay remains removed.
- Check the resistance between contact 1 and contact 4 of the 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 relay has failed.
Repair: Replace the relay.
Stop.
Test Step 3. CHECK THE SIGNAL CIRCUIT OF THE RELAY FOR A SHORT TO +BATTERY
- Disconnect the machine harness connectors J1 and J2 from the ECM.
- At the J1 and J2 machine harness connectors for the ECM, measure the resistance from the signal contact of the relay J2-5 (wire 321-BR) to all possible sources of +battery.
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
- Disconnect the machine harness from the backup alarm.
- At the connector of the backup alarm measure the resistance between contact 1 of the connector (wire 612-GY) to all possible sources of +battery.
Expected Result:
Each resistance should be greater than 5 ohms.
Results:
- YES - The resistance is greater than 5 ohms. The ECM may have failed. 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.
- Turn the battery disconnect switch and the key start switch to the ON position.
- 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 ECM may have failed.
Repair: It is unlikely that the ECM has failed. Exit this procedure and perform this procedure again. If the cause of the fault is not found, replace the ECM. Refer to Systems operation, Troubleshooting, Testing and Adjusting, "Electronic Control Module (ECM) - Replace" for the machine that is being serviced.
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.