24H Motor Grader Transmission Electronic Control System And Hydraulic Calibrations Caterpillar

Illustration 1	g00494026
Schematic For Start Relay

This fault is recorded when there is an open circuit in the signal wire to the relay or the return wire to the ECM. The start relay is located in the relay panel on the right rear side of the engine compartment. Connector J1-8 (wire 306-GN), connector J1-7 (wire 975-WH), and connector J2-3 (wire 975-WH) relate to this detected fault. The engine does not crank as a result of this fault condition.

1. CHECK THE RELAY FOR AN OPEN.

   1. The key start switch and the disconnect switch remain in the OFF position.

   2. Disconnect the machine harness connector from the start relay.

   3. At the relay, measure the resistance between the two contacts of the relay.

      Expected Result: The resistance should be between 25 - 30 ohms.

      Results:

      • OK - The machine harness circuit resistance is correct. Go to Step 2.

      • NOT OK - Resistance is not correct. The coil in the relay is faulty. Replace the start relay. STOP.

2. CHECK THE GROUND CIRCUIT OF THE HARNESS.

   1. The key start switch remains OFF and the start relay remains disconnected from the machine harness.

   2. At the machine harness connector for the start relay, measure the resistance from contact 2 (wire 975-WH) to frame ground.

      Expected Result: The resistance is less than 5 ohms.

      Results:

      • Resistance is less than 5 ohms. The ground circuit is correct in the machine harness. Go to Step 3.

      • Resistance is greater than 5 ohms. The machine harness is faulty. Wire 975-WH is open in the machine harness. Repair the machine harness or replace the machine harness.

3. CHECK THE CONTINUITY OF THE HARNESS.

   1. The key start switch remains OFF.

   2. Reconnect the start relay to the machine harness.

   3. Disconnect the machine harness connector from the ECM. Identify connector J1-8 (wire 306-GN) and J1-7 (wire 975-WH).

   4. At the machine harness connector for the ECM, measure the resistance from J1-7 to J1-8.

      Expected Result:The resistance measures 25 - 30 ohms.

      Results:

      • The resistance is 25 to 30 ohms. Go to Step 4.

      • The resistance is NOT 25 to 30 ohms. Wire 306-GN or wire 975-WH is not correct in the machine harness. Repair the machine harness or replace the machine harness.

4. CHECK IF THE FAULT IS STILL PRESENT.

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

   2. Reconnect all harness connectors.

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

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

   5. Operate the machine. Watch for a recurrence of the fault.

   6. Check if the CID 0444 FMI 05 service code is active.

      Expected Result: The CID 0444 FMI 05 for the relay is active.

      Results:

      • YES - The fault has not been corrected. It is unlikely that the ECM is faulty. Perform the previous steps again. If the cause of the fault is not found, replace the ECM. See Testing and Adjusting, "Electronic Control Module (ECM) - Replace". STOP.

      • NO - Fault is NOT active. The fault does not exist at this time. The initial fault was probably caused by a poor electrical connection or a short at one of the harness connectors that was disconnected and reconnected. Resume normal machine operation. STOP.