Use this procedure to troubleshoot any suspect problems with the machine indicator lamps.
The indicator lamps are activated by the Electronic Control Module (ECM) to inform the operator of various conditions. When the key switch is in the ON position, the diagnostic lamp and warning lamp are illuminated by the ECM for a brief period.
The ECM provides a high side driver for all of the lamp outputs. The most likely cause of a problem with an indicator lamp is the bulb. The next most likely cause is a problem with a wire or with a connector. The least likely cause is a problem with the ECM.
Note: An override feature is available in Cat® Electronic Technician (ET) for each of the lamp circuits. The override can be used to troubleshoot the lamp circuits.
When following the instructions below, refer to the latest revision of the electrical schematic. The electrical schematics for specific machine models are listed below:
- The electrical schematic for model 621K is Electrical Schematic , KENR9577.
Note: Poor harness connections are often the cause of a problem in electrical circuits. Before performing any troubleshooting procedure, inspect all of the connectors involved in the circuit. Verify that all of the connections in the circuit are dry, clean, secure, and in good condition. Each pin and socket in the connectors should mate correctly when the connectors are fastened together. Check for exposed wires at the connectors for nicks or abrasion. If a problem is found with any of the connections: correct the problem and verify that diagnostic code is still active, before performing the following procedures. For more information, refer to Troubleshooting, "Electrical Connector - Inspect".
|Troubleshooting Test Steps||Values||Results|
|1. Inspect The Electrical Connectors And The Wiring.
A. Remove electrical power from the impacted ECM.
B. Thoroughly inspect any of the connectors that are associated with the lamp circuits. Refer to the schematic for your machine for connector locations. Refer to Troubleshooting, "Electrical Connector - Inspect".
C. Perform a
D. Check the harness and the wiring for abrasion and for pinch points from the dash display back to the ECM.
Contacts are in good condition.
|OK- The harness and connectors appear to be in good repair.
Proceed to Test Step 2.
NOT OK- The connectors and/or wiring need repair.
Repair: The wiring and/or the connectors. Replace parts, if necessary. Ensure that all of the seals are properly in place and ensure that the connectors are coupled. Verify that the repair eliminates the problem.
|2. Check For Proper Operation Of The Lamp Circuits.
A. Connect Cat ET to the service tool connector.
B. Restore electrical power to the ECM.
C. Select the "Override Parameters" option from the "Diagnostic Tests" on Cat ET.
D. Use the correct override parameter to power the circuit for the suspect lamp.
E. Remove electrical power from the ECM.
Lamp circuits are correct.
|OK- The suspect lamp illuminates when the override is on.
Repair: There does not appear to be a problem with the lamp circuit at this time. The problem may have been related to a faulty connection in the harness. Carefully reinspect the connectors and wiring. Refer to Troubleshooting , " Electrical Connector - Inspect".
NOT OK- The suspect lamp does not illuminate when the override is on.
Inspect the lamp and the lamp socket for the suspect circuit. If either of the components are questionable, replace the component. Retest the circuit. If the problem persists or if the components of the lamp assembly appear to be in good repair, proceed to the next test step.
Proceed to Test Step 3.
|3. Use The Override to Check the Wiring Harness.
A. Remove the lamp for the suspect circuit from the lamp socket.
B. Connect a test lamp between the terminal that is for the driver circuit from the ECM and the −Battery terminal.
C. Restore electrical power to the ECM.
D. Use the override parameter in Cat ET to power the circuit for the suspect lamp.
E. Remove electrical power from the ECM.
Test lamp is working correctly.
|OK- The test lamp illuminates when the override is turned on.
Repair: Check for continuity between the negative terminal of the lamp socket and −Battery.
If the circuit is continuous, the lamp or the lamp socket is the cause of the problem. Replace the faulty lamp or the faulty lamp socket. Verify that the repair eliminates the original problem.
If the circuit is not continuous, there is a problem in the ground circuit for the lamp. Repair the ground circuit. Verify that the repair eliminates the original problem.
NOT OK- The test lamp does not illuminate when the override is turned on. There is a problem in the harness or in a connector. There may be a problem with the ECM.
Proceed to Test Step 4.
|4. Check For Proper Operation Of The ECM.
A. Ensure that electrical power has been removed from the ECM.
B. Disconnect the ECM connectors for the suspect lamp circuit.
C. Remove the signal wire for the suspect lamp from the ECM connector.
D. Fabricate a jumper wire that is long enough to create a test circuit between the ECM connector and the negative battery connection. Crimp a connector socket to one end of the jumper wire.
E. Install the socket end of the jumper wire into the terminal location that is for the signal wire of the suspect lamp.
F. Reconnect the ECM connectors.
G. Connect a test lamp between the loose end of the jumper wire and −Battery.
H. Restore electrical power to the ECM.
J. Use the override parameter in Cat ET to power the circuit for the suspect lamp.
K. Remove electrical power from the ECM. Restore all wiring to the original configuration.
The test lamp illuminates when the override is on.
|OK- The test lamp illuminates when the override is on.
Repair: The ECM is operating correctly. There is a problem in the harness or in a connector. Repair the harness and/or the connector or replace the harness and/or the connector. If necessary, replace parts. Verify that the repair eliminates the problem.
NOT OK- The test lamp does not illuminate when the override is on.
Repair: The harness for the lamp circuit is OK. The ECM is not powering the lamp circuit correctly. Replace the ECM. Refer to Troubleshooting, "ECM - Replace" for details.