AIR COMPRESSOR GP 3843633 - Caterpillar

that all connections are clean, secure, and in good condition.Find the open circuit or poor connection in the data link circuits to resolve this problem.STOPTest Step 2. CHECK THE RESISTANCE OF THE DATA LINK CIRCUITThe key switch and the battery disconnect switch remain in the OFF position. The low voltage compartment covers are removed.The jumper wire that was connected in the last test step has been removed.The Drivetrain ECM J2 harness connector remains disconnected and the Motor 1 ECM J1 connector remains disconnected.
At the disconnected harness connector J2 for the Drivetrain ECM, measure the resistance between CAN B+ contact J2-64 (wire Y959-YL(Yellow)) and CAN B- contact J2-65 (wire Y960-GN(Green)).Expected Result:The resistance measurement is approximately 60 ohms.Results:
OK - The resistance measurement is approximately 60 ohms. The resistance measurement is indicating that the terminating resisters are connected to the circuits and the resisters are not faulty. Proceed to Test Step 3.
NOT OK - The resistance measurement is not approximately 60 ohms. There is a problem with one or both of the terminating resisters.Repair: If the resistance between the data link circuits is approximately 120 ohms, one of the terminating resisters is not connected or is faulty.If the resistance of the data link circuit is much less than 60 ohms, both of the terminating resisters are not connected or are faulty.Isolate the section of the circuit where the open circuit is located by disconnecting the machine harness connector CX-C4 from the cabinet connector CN2. Measure the resistance of the CN2 data link circuits that enter the cabinet. Measure the resistance of the CX-C4 data link circuits that go out to the Drivetrain ECM. These circuit connections are illustrated in the diagram at the beginning of this procedure. Each resistance measurement should be approximately 120 ohms since each measurement is through one of the resisters.If one of the resistance measurements is not correct, disconnect the individual terminating resister and check the resistance. Replace the resisters if the measurement is not approximately 120 ohms.STOPTest Step 3. CHECK THE DATA LINK CIRCUIT FOR A SHORTNote: A short circuit in the system would most likely cause all the control modules in the system to activate this diagnostic code. However, since no open circuits or poor connections have been found, a short circuit could be causing the problem.The key switch and the battery disconnect switch remain in the OFF position.The Drivetrain ECM J2 harness connector remains disconnected and the Motor 1 ECM J1 connector remains disconnected.
At the Motor 1 ECM, disconnect the J2 harness connector.
At the Motor 1 ECM, measure the resistance between the CAN B positive circuit at contact J1-66 (wire CANBH) and a good cabinet ground point. Measure the resistance between the CAN B positive circuit contact J1-66 and all the other circuits (except CAN B negative circuit contact J1-67) that are used in the Motor 1 ECM J1 and J2 connectors.Expected Result:Each individual resistance measurement between the CAN B circuit and the other Motor 1 ECM circuits is greater than 4000 ohms.Results:
OK -