VALVE GP-MAIN CONTROL 1851439 - Caterpillar

This diagnostic code is for the sensor supply of the transmission oil temperature sensor or the steering oil temperature sensor.Both sensors are never present on the same machine. Refer to the Electrical System Schematic for the machine that is being serviced in order to determine the sensor that is on the machine.This diagnostic code is recorded when the voltage of the supply circuit for the sensor (709-OR(Orange)) is below the normal range. The transmission oil temperature sensor or the steering oil temperature sensor will not operate. The transmission may not shift smoothly when the transmission oil is cold (medium tractors). Top brake pressure will be reduced to a pressure near the pressure at brake touch up and the brakes may drag lightly. The possible causes of this diagnostic code are listed below:
The supply circuit (709-OR(Orange)) to the sensor is shorted to ground.
The sensor has failed.
The ECM has failed. This is unlikely. Ensure that the CID 0269 FMI 04 is on hold and that the diagnostic code indicator shows "SERV CODE". This procedure can cause a CID 0177 FMI 03. This procedure can cause a CID 0075 FMI 03. Ignore these created problems. When the procedure is completed, clear the created problems. Test Step 1. CHECK THE SENSOR.
Turn the key start switch to the ON position.
Access Service Mode. Place CID 0269 FMI 04 on hold. Ensure that the diagnostic code indicator shows "SERV CODE". See Testing and Adjusting, "Using Caterpillar Monitoring System to Determine Diagnostic Codes".
While you observe the status of the diagnostic code indicator or you listen for the sounding of the action alarm, disconnect the machine harness from the sensor. Expected Result:If the sensor is not the cause of the problem, "SERV CODE" remains ON. If the sensor has failed, "SERV CODE" goes OFF. Results:
OK - "SERV CODE" remains ON. The sensor has not failed. The machine harness or the ECM may have failed. Proceed to Test Step 2.
NOT OK - "SERV CODE" goes OFF.Repair: The machine harness and the ECM are operating properly. The sensor has failed. Replace the sensor.STOPTest Step 2. CHECK THE SUPPLY CIRCUIT FOR A SHORT TO GROUND.
The sensor remains disconnected from the machine harness.
Turn the key start switch to the OFF position.
Disconnect the machine harness connectors J1 and J2 from the ECM.
At machine harness connector J2, measure the resistance from contact J2-12 ( sensor supply) to all possible sources of ground. The possible sources of ground are contact J1-2, contact J1-5, contact J1-7, contact J1-15, contact J1-16, contact J2-3 and frame ground. Expected Result:Each resistance should be greater than 5000 ohms.Results:
OK - Each resistance is greater than 5000 ohms. The machine harness is correct. Proceed to Test Step 3.
NOT OK - Each resistance is not greater than 5000 ohms.Repair: There is a short in the machine harness. The short is between J2-12 (709-OR(Orange)) and a ground source. The possible ground sources are contact J1-2 (202-BK(Black)), contact J1-5 (202-BK(Black)), contact J1-7 (975-WH(White)), contact J1-15 (G939-PK(Pink)),