ENGINE AR 7W9478 - Caterpillar

Which Generate This Code:This fault is indicated when the ECM detects an incomplete path in the electrical circuit. The open circuit is in the path from the control to the solenoid. If the open condition exists, the control shifts the machine to neutral instead of the forward direction. Connector contact 31 relates to this fault.Note: The following steps may create other indicated faults. Clear these faults when the original fault is corrected.Test Step 1. CHECK THE SOLENOID VALVE
Turn the start switch to the OFF position.
Disconnect the faulty solenoid from the machine harness.
Measure the resistance at the solenoid. Measure the resistance from contact 1 to contact 2.Expected Result:The resistance should be 20 ohms to 25 ohms.Results:
NO - The resistance is not 20 ohms to 25 ohms.Repair: The solenoid is faulty. Replace the solenoid. Stop.
YES - The resistance is 20 ohms to 25 ohms. Proceed to test step 2.Test Step 2. CHECK THE GROUND CIRCUIT
Check the continuity on the harness connector for the faulty solenoid. Check the continuity from contact 2 to frame ground.
The frame ground must be reliable.Expected Result:The resistance is greater than 5 ohms or the resistance is less than 5 ohms.Results:
YES - The resistance is greater than 5 ohms. There is an open wire in the harness. Proceed to test step 3.
YES - The resistance is less than 5 ohms. Proceed to test step 4.Test Step 3. CHECK THE GROUND INTERRUPT RELAY
Check the relay contacts. The contacts should be closed.
If the relay contacts are open, a fault will be shown.Results:
YES - The contacts are closed.Repair: Check the wiring to the relay socket. Check the wiring from the relay socket. There should be continuity from the solenoid harness through the ground interrupt relay. There should be continuity to contact 39 of the harness connector. Stop.
NO - The contacts are open. The relay is faulty. Replace the relay. Stop.Test Step 4. CHECK THE HARNESS
Reconnect all solenoid connectors.
Disconnect the harness connector from the control.
Measure the resistance at the harness connector for the machine. Measure the resistance from the faulty output circuit to contact 39.Expected Result:The resistance should be 20 ohms to 25 ohms.Results:
NO - The resistance is greater than 5000 ohms. The signal wire in the machine harness is open.Repair: Repair the harness or replace the harness. Stop.
YES - The resistance is 20 ohms to 25 ohms. The cause of the fault is not found. Proceed to test step 5.Test Step 5. CHECK IF THE FAULT REMAINS
Inspect all harness connectors.
Reconnect all harness connectors.
Turn the start switch to the ON position.
Enter the service mode.
Operate the machine.
Check if the same fault is active.Results:
YES - The fault has not been found.Repair: Perform the previous steps again. If the cause of the fault is not found, replace the ECM. Stop.
NO - The fault is not active or the fault does not exist at this time. The fault was probably caused by a poor connection in the harness. Resume normal machine operation. Stop.