ELECTRONICS GP-MONITOR 2882502 - Caterpillar

Machine ECM
The following is a list of Diagnostic Trouble Codes (DTCs) that are associated with the relays of the machine.
Table 1
Machine ECM (MID 299)
DTC Code Description System Response
781-3 Lighting Relay : Voltage Above Normal Related lighting system will be ON continuously.
781-6 Lighting Relay : Current Above Normal Related lighting system will be ON continuously.
2912-3 Front Wiper Speed Control Relay : Voltage Above Normal Wiper system will not function.
2912-6 Front Wiper Speed Control Relay : Current Above Normal Wiper system will not function.
3634-3 Boom Light Relay : Voltage Above Normal Related lighting system will be ON continuously.
3634-6 Boom Light Relay : Current Above Normal Related lighting system will be ON continuously. A relay is a component that uses a small amount of electrical current to control a large amount of electrical current. Possible causes for an FMI 3 diagnostic code are:
The signal circuit is shorted to +battery.
The relay has failed.
The ECM has failed. A failure of the ECM is unlikely.Possible causes for an FMI 6 diagnostic code are:
A short to ground exists.
The relay has failed.
The ECM has failed. A failure of the ECM is unlikely.
Illustration 1 g03732238
Schematic of the relay circuits associated with the Switch Panel
Note: The diagram above is a simplified schematics of the relay connections. The schematic is electrically correct. However, not all of the possible harness connectors are shown. Refer to the latest revision of Electrical Schematic, UENR5907 for the complete schematic.Diagnostic Trouble Code Procedure
Note: Prior to beginning this procedure, inspect the harness connectors that are involved in this 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. Check the wiring harness for pinch points or abrasions. Look for and repair areas that indicate wires are exposed. If a problem with a connection is found, correct the problem and verify that the diagnostic code is active before performing a troubleshooting procedure.
Identify the active FMI code associated with the components.
Determine which code is present and use the list below to determine which procedure to follow.
FMI 3 diagnostic code, proceed to Table 2.
FMI 6 diagnostic code, proceed to Table 3.
Table 2
FMI 3 Troubleshooting
Troubleshooting Test Steps Values Results
1. Check The Machine Harness For A Short
A. Turn the key start switch and disconnect switch OFF.
B. Disconnect the relay from the harness.
C. Disconnect the ECM machine harness connectors.
D. At the ECM machine harness connector, measure the resistance between the signal contact and all other contacts that are used in the ECM.
Each resistance measurement is greater than 5Ω. OK - All resistance measurements are greater than 5 Ω.
Proceed to Test Step 2.
NOT OK - One or more readings are less than 5 Ω.
Repair: A short exists between the signal contact and the circuit with the low resistance. Repair or replace the machine harness.
Note: A resistance that is greater than 5 Ω but less than 5K Ω would indicate a loose connection or a corroded connection in the circuit. A resistance measurement that is