ALTERNATOR G 2Y7775 - Caterpillar

Illustration 1 g00592497
Schematic for Magnetic Switch for the Start RelayThis diagnostic code is recorded when the power train ECM detects an incomplete electrical path. The electrical path from the ECM to the solenoid back to the ECM is incomplete.Possible causes of this diagnostic code are listed:
The harness has failed.
The solenoid is shorted to ground.System Response:The machine response is listed:
The engine will not start.Note: This procedure can cause new diagnostic codes to be recorded. Ignore these created diagnostic codes. Complete the following procedure. Then clear the created diagnostic codes.Note: Ensure that the diagnostic code is active and that the diagnostic code indicator is active.Test Step 1. Check the Solenoid.
Turn the battery disconnect switch and the key start switch to the ON position.
Disconnect the solenoid from the harness.
Observe the ON/OFF status of the diagnostic code indicator.
At the harness connector for the solenoid, place a jumper from contact 1 to contact 2.Expected Result:The diagnostic code indicator should remain active.Results:
YES - The diagnostic code indicator remains active.Repair: The harness or the power train ECM has failed. Proceed to test step 2.
NO - The diagnostic code indicator changes from the active mode to the inactive mode.Repair: The solenoid or the harness has failed. Repeat Step 1 in order to verify that the solenoid has failed. Repair the solenoid and/or the harness or replace the solenoid and/or the harness. Stop.Test Step 2. Check for an Open Harness Circuit.
Turn the disconnect switch to the OFF position.
Remove the jumper that was installed in the previous test step.
Reconnect the solenoid to the harness.
Disconnect the harness from the ECM.
At the harness connector for the power train ECM, measure the resistance between wire 975-WH and the contact for the failed solenoid circuit.Expected Result: The resistance should be between 6 to 14 Ohms.Results:
YES - The resistance is between 6 to 14 ohms.Repair: It is unlikely that the power train ECM has failed. Perform these test steps again. Also ensure that the diagnostic code indicator is active for this diagnostic code. If the cause is not found, replace the power train ECM. Stop.
NO - The resistance is greater than 5000 Ohms.Repair: The harness circuit has failed. Wire 975-WH is open in the harness between the ECM and the solenoid, or the wire to the solenoid is open. Repair the harness or replace the harness. For additional information on replacing the power train ECM, refer to Testing and Adjusting, "Electronic Control Module (Power Train ) - Replace". Stop.