KNOB 3C8431 - Caterpillar

Illustration 1 g01189071
Schematic of the Circuit for the Downshift Solenoid
This diagnostic code is recorded when the ECM reads the current of the solenoid as being above normal.The possible causes are listed:
A wire is shorted to ground.
The solenoid has failed.
The ECM has failed. This is unlikely.Note: The following procedure can create numerous related diagnostic codes. When all harnesses are reconnected, the related diagnostic codes will be shown as being not active. Clear all related diagnostic codes after this procedure is completed.System Response:The transmission will not shift because the solenoid is NEVER ON.Test Step 1. CHECK THE SOLENOID.
Turn the disconnect switch and the key start switch to the ON position. DO NOT start the engine.
Disconnect the machine harness from the solenoid.
At the machine harness connector for the solenoid, place a jumper wire from contact 1 (wire 704-GY(Grey)) to contact 2 (wire K972-BR(Brown)).
Observe the status of the diagnostic code. Expected Result:The diagnostic code is active. Then, the diagnostic code is NOT active as the jumper wire is installed and removed. Results:
YES - The circuit is correct. The solenoid has failed.Repair: Repeat this test "CHECK THE SOLENOID" in order to verify that the solenoid has failed. Replace the solenoid.STOP
NO - The diagnostic code remains active. Proceed to test step 2.Test Step 2. CHECK THE SOLENOID CIRCUIT FOR A SHORT TO GROUND.
The machine harness remains disconnected from the solenoid.
Turn the key start switch and the disconnect switch to the OFF position.
Disconnect the J1 and J2 machine harness connector from the ECM.
At the J1 machine harness connector, measure the resistance from the solenoid contact J1-12 (wire 704-GY(Grey)) to all possible sources of ground. The possible sources of ground are listed: J1-3, J1-5, J1-7, J1-13, J1-20, J1-23, J1-57, J1-60, J1-70, J2-22, J2-63 and frame ground. Expected Result:Each resistance measurement should be greater than 5000 ohms.Results:
YES - The machine harness is correct. Proceed to test step 3.
NO - There is an short in the machine harness.Repair: The short is between the wire for the solenoid signal and the circuit with the low resistance measurement. Repair the machine harness or replace the machine harness.STOPTest Step 3. CHECK IF THE DIAGNOSTIC CODE REMAINS.
Inspect the contacts and clean the contacts of the harness connectors.
Reconnect all harness connectors.
Turn the disconnect switch and the key start switch to the ON position.
Clear all inactive diagnostic codes.
Operate the machine.
Stop the machine and set the transmission control to the PARK position.
Check if the diagnostic code for the solenoid is active. Expected Result:The diagnostic code is NO longer active. Results:
YES - The diagnostic code is NO longer active. The diagnostic code does not exist at this time. The initial diagnostic code 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
NO - The diagnostic code has not been corrected.Repair: It is unlikely that the ECM has failed. Exit this procedure and perform this procedure again. Verify that the diagnostic code is active. If the cause of the diagnostic code is