TUBE AS 1324255 - Caterpillar

Operation Description:The main display module is unable to identify system errors in simple circuits. No service code is available in order to assist the operator with troubleshooting. A possible failure exists when the operation of an alert indicator does not correspond to a known condition of the machine. For example, the alert indicator never FLASHES regardless of the actual pressure of the engine oil. Before you start troubleshooting, ensure that a problem exists. For a description of normal conditions that cause these events, see the Operation and Maintenance Manual for the machine that is being serviced. Perform the following procedures only if a failure is suspected. The indicator reflects the open or grounded condition of the switch inputs. When a switch input is open, the corresponding alert indicator FLASHES. When a switch input is grounded, the corresponding alert indicator is OFF. Therefore, in order to check a circuit, the service person opens the switch. Then, the service person grounds the switch. This is done while the service person is watching for the correct result on the alert indicator. Test Step 1. LOCATE THE SWITCH
Locate the switch for the alert indicator that never flashes. (If necessary, use the Electrical System Schematic to assist in locating the switch.)Expected Result:The switch is located.Results:
OK - The switch is located. Proceed to test step 2.Test Step 2. CHECK THE HARNESS.
Disconnect the signal wire from the switch.Expected Result:The alert indicator is FLASHING.Results:
YES - The alert indicator FLASHES. The circuit is operating correctly. The switch has failed.Repair: Repair the switch or replace the switch.STOP
NO - The alert indicator does NOT FLASH. The circuit has failed. The signal wire is probably shorted to ground. Proceed to test step 3.Test Step 3. CHECK THE HARNESS
Turn the disconnect switch and the key start switch to the OFF position.
The signal wire remains disconnected from the switch. Do not allow the signal wire to touch any objects.
On the Electrical System Schematic, trace the signal wire from the switch to the main display module.
Determine the signal contact (connector contact) of the machine harness at the main display module.
Disconnect the machine harness from the main display module.
At the machine harness connector for the display module, check for continuity between the signal contact and contact 2 or frame ground if a ground wire is not present at contact 2.Expected Result:The resistance is greater than 5000 ohms.Results:
YES - The resistance is greater than 5000 ohms. The harness is not causing the failure. The main display module has failed.Repair: It is unlikely that the main display module has failed. Exit this procedure and perform this procedure again. Also, recheck if the diagnostic code indicator is illuminated for this diagnostic code. If the cause of the diagnostic code is not found, replace the main display module. See Testing and Adjusting, "Module - Replace". STOP
NO - The resistance is less than 5000 ohms. The harness has failed. The signal wire within the harness is shorted to ground.Repair: Repair the harness or replace the harness.STOP