D250E Series II, D300E Series II, D350E Series II and D400E Series II Articulated Trucks Power Train Electronic Control System Caterpillar

Illustration 1	g00482452
Schematic Of The Start Relay

This diagnostic code is recorded when the ECM reads the voltage of the relay circuit as above normal (short to +battery).

The possible causes of this diagnostic code are listed:

• Wire 306-GN shorted to +battery.

• The relay is faulty.

• The ECM is faulty.

Note: Ensure that the CID 0444 FMI 03 for the relay is active.

This diagnostic code indicates that the start relay is energized at all times.

1. CHECK THE SIGNAL CIRCUIT FOR A SHORT TO +BATTERY.

   1. Turn the key start switch and the disconnect switch to the OFF position.

   2. Disconnect the relay with the diagnostic code from the machine harness.

   3. Disconnect the machine harness connectors J1 and J2 from the ECM.

   4. At the machine harness connector J1 and J2, measure the resistance from signal contact J1-8 (wire 306-GN) to all possible sources of +battery. The possible sources of positive voltage are connectors: J1-1 (wire 126-PK), J1-4 (wire A958-WH), J1-6 (wire 126-PK), J1-8 (wire 306-GN), J1-10 (wire 728-BU), J1-11 (wire 708-PK), J1-12 (wire 703-BU), J1-17 (wire 904-BU), J1-18 (wire 704-GY), J2-1 (wire K746-PK), J2-2 (wire 366-OR), J2-7 (wire G870-GY), J2-8 (wire K745-YL), J2-13 (wire G705-GN), J2-19 (wire G704-YL) and J2-37 (wire 321-BR).

      Expected Result: Each resistance measurement should be greater than 5000 ohms.

      Results:

      • YES - The machine harness is correct. Proceed to 2.

      • NO - The resistance is not correct. There is a short in the machine harness. The short is between the signal contact J1-8 (wire 306-GN) and the circuit with the low resistance measurement. Repair the harness or replace the harness. STOP.

2. CHECK IF THE DIAGNOSTIC CODE REMAINS.

   1. Inspect the contacts and clean the contacts of the harness connectors.

   2. Reconnect all harness connectors.

   3. Turn the key start switch and the disconnect switch to the ON position.

   4. Enter the service mode of the Caterpillar Monitoring System and clear all the inactive diagnostic codes.

   5. Operate the machine.

   6. Observe the status of the "SERV CODE" indicator.

      Expected Result: The CID 0444 FMI 03 for the relay is NO longer present. The "SERV CODE" is not showing.

      Results:

      • YES - The diagnostic code is NO longer present. The "SERV CODE" is not showing. The diagnostic code does not exist at this time. The initial diagnostic code was probably caused by a poor electrical connection at one of the harness connectors that was disconnected and reconnected. Resume normal machine operation. STOP.

      • NO - It is unlikely that the ECM is faulty. Exit this procedure and perform this procedure again. If the cause of the diagnostic code is not found, replace the ECM. See Testing And Adjusting, "Electronic Control Module (ECM) - Replace". STOP.