CYLINDER AS 6E1550 - Caterpillar

Illustration 1 g03476470
Schematic of the Backup Alarm
When the shift lever 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 J2-2 (wire A626-GN(Green)), 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 A16 (wire 104-YL(Yellow)), 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. This situation is unlikely.Note: The diagram above is simplified schematic of the relay connections for the Backup Alarm. The schematic is electrically correct. However, not all of the possible harness connectors are shown. For the complete schematic information reference Electrical Schematic , UENR3118, "950 GC Wheel Loaders".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 contact J2-2 (wire A626-GN(Green)) 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 A626-GN(Green) 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 contact 1 (wire 321-BR(Brown)) and fuse location A16.
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 Testing and Adjusting, "Electronic Control Module (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