PLATE-LOCK 1356104 - Caterpillar

Diagnostic Trouble Code (DTC) Root Causes
When the Transmission Control is in the REVERSE position, a signal is sent to the Transmission Electronic Control Module (ECM). The Transmission ECM reacts to this signal by energizing the Backup alarm. Transmission ECM location J1-12 (wire 331-OR(Orange)), supplies power to the backup alarm relay coil. When the backup alarm relay is energized, +battery is applied to the backup alarm. Fuse panel location G12 (wire 121-RD(Red)), supplies power to the backup alarm relay.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 ECM has failed.Electrical Information and Schematic
Illustration 1 g06206906
Schematic of the backup alarm
Note: The diagram above is simplified schematic of the relay connections for the Backup Alarm. The schematic is electrically correct. However, not all the possible harness connectors are shown. For the complete schematic information reference one of the documents below (depending on your machine configuration).Refer to the latest revision of the Electrical Schematic, UENR4170, "740 Ejector and 745 Articulated Truck (HRC) Electrical System".Refer to the latest revision of the Electrical Schematic, UENR4171, "740 Ejector and 745C Articulated Truck (LRC) Electrical System".Troubleshooting Procedure
Note: Prior to beginning this procedure, inspect the harness connectors that are involved in the circuit. Poor connections can often be the cause of a problem in an electrical circuit. Verify that all connections in the circuit are clean, secure and in good condition. If a problem with a connection is found, correct the problem and verify that this diagnostic code is active before performing this procedure.
Table 1
Troubleshooting Test Steps Values Results
1. Check For A Shorted Harness
A. Turn the key start switch and the battery disconnect switch to the OFF position.
B. Disconnect the backup alarm relay.
C. Disconnect the backup alarm from the harness.
D. At the harness connector for the backup alarm, measure the resistance between wire612-GY(Grey)and all other possible sources of +battery.
Each resistance is greater than 5K Ω. OK - Each resistance is greater than 5K Ω. The resistance to the harness circuit is correct.
Proceed to Test Step 2.
NOT OK - A resistance measurement is less than 5K Ω. The harness has failed. The corresponding wire is shorted to wire 612-GY(Grey)within the harness.
Repair- Repair the harness or replace the harness.
2. Check For A Shorted Relay
A. Reconnect the relay. The backup alarm harness connector remains disconnected.
B. At the harness connector for the backup alarm, measure the resistance between wire 612-GY(Grey)and fuse location G12.
The resistance should be greater than 5K Ω. OK - The resistance measurement is greater than 5K Ω. The resistance of the harness through the relay is correct. Failure of the ECM is unlikely.
Repair- If the cause is not found, replace the ECM. See Troubleshooting, "ECM - Replace".
NOT OK - The resistance is less than 5K Ω. There is continuity through the relay. The relay is shorted.
Repair: The relay for the Backup Alarm has failed, replace the relay.
STOP