797 and 797B Off-Highway Truck Power Train Electronic Control System Caterpillar

This diagnostic code is recorded when the signal circuit of the requested gear command is shorted to ground. The circuit is a single wire that connects the chassis ECM to the transmission ECM. Wire (J883-BU(Blue)) is connected to contact J2-33 of the chassis ECM and contact J1-16 of the transmission ECM.

Test Step 1. CHECK THE SIGNAL CIRCUIT FOR A SHORT TO GROUND

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

   2. Disconnect the J1 machine harness connector from the transmission ECM.

   3. Disconnect the J1 machine harness connector from the chassis ECM.

   4. At the J1 machine harness connector for the transmission ECM, measure the resistance from contact J1-16 (wire J883-BU(Blue)) to all sources of ground. The sources of ground are contacts: J1-9, J1-12, J2-2, J2-12, J2-13, J2-18, J2-22, J2-36, J2-46, J2-49, J2-52, J2-56, J2-59, J2-69 and frame ground.

Expected Result:

Each resistance measurement should be greater than 5000 ohms.

Results:

• YES - Each resistance measurement is greater than 5000 ohms. The harness is correct. Clean all harness connectors that were disconnected. Reconnect all harness connectors and verify that the diagnostic code is no longer present. The diagnostic code was probably caused by a poor electrical connection.

  Repair: If the cause of the diagnostic code is not found, replace the transmission ECM. Ensure that replacement of the ECM is absolutely necessary. See Testing and Adjusting, "Electronic Control Module (ECM) - Replace".

  STOP

• NO - One or more resistance measurements is not greater than 5000 ohms. There is a short in the machine harness. The short is in the circuit (s) with the low resistance measurement. Repair the machine harness or replace the machine harness. Verify that the repair corrects the problem.

  STOP