PUMP & MOTOR GP-SEC STEERING 2379874 - Caterpillar

Table 1
Steering Pump Oil Pressure Sensor 1 Signal Voltage versus Pressure
Pressure Signal Voltage Pressure Signal Voltage
6895 kpa (1000 psi) 0.9 VDC 24.1 mpa (3500 psi) 2.9 VDC
13.8 mpa (2000 psi) 1.7 VDC 25.6 mpa (4000 psi) 3.3 VDC
17.2 mpa (2500 psi) 2.1 VDC 31.0 mpa (4500 psi) 3.7 VDC
20.7 mpa (3000 psi) 2.5 VDC 34.5 mpa (5000 psi) 4.0 VDC Possible causes of the diagnostic code are listed below:
The supply circuit is open.
The return circuit is open.
The signal circuit is shorted to another power source.
The signal circuit is open or the sensor is disconnected.
The sensor has failed.
The ECM has failed. This condition is unlikely.Note: Ensure that the CID 3652 FMI 03 diagnostic code is active. This procedure can cause new diagnostic codes to be recorded. Ignore these created diagnostic codes. When the procedure is completed, clear the created diagnostic codes.Test Step 1. CHECK THE VOLTAGE AT THE SENSOR
Turn the disconnect switch and the key start switch to the ON position.
Disconnect the sensor from the machine harness.
At the machine harness connector for the sensor, measure the voltage between contact 1 (wire T786-OR(Orange)) and contact 2 (wire R998-BR(Brown)). Expected Result:The voltage measurement is approximately 5 VDC.Results:
OK - The voltage measurement is approximately 5 VDC. Proceed to test step 4.
NOT OK - The voltage is not approximately 5 VDC. There is an open in the machine harness or the ECM has failed. The failed condition of the ECM is unlikely. Proceed to test step 2.Test Step 2. CHECK FOR AN OPEN IN THE SUPPLY CIRCUIT
The key start switch and the disconnect switch remain in the ON position.
The sensor remains disconnected from the machine harness.
At the machine harness connector for the sensor, measure the voltage from contact 1 (wire T786-OR(Orange)) to ground. Expected Result:The voltage measurement is approximately 5 VDC.Results:
OK - The voltage measurement is approximately 5 VDC. Proceed to test step 3.
NOT OK - The voltage does not measure approximately 5 VDC. The supply circuit is not correct.Repair: Repair the circuit or replace the circuit.STOPTest Step 3. CHECK FOR AN OPEN IN THE RETURN CIRCUIT.
Turn the key start switch and the disconnect switch to the OFF position.
The sensor remains disconnected from the machine harness.
Disconnect the machine harness connector J1 from the Implement ECM.
At the machine harness connector for the sensor, install a jumper wire from contact B (wire R998-BR(Brown)) to ground.
At the machine harness connector for the Implement ECM, measure the resistance from contact J1-21 (wire R998-BR(Brown)) to ground. Expected Result:The resistance measurement is less than 5.0 ohms.Results:
OK - The resistance measurement is less than 5.0 ohms. The harness is correct. The Implement ECM may have failed.Repair: The failed condition of the ECM is unlikely. Recheck the status of the diagnostic code. If the diagnostic code remains present, exit this procedure and perform this procedure again. If the cause of the diagnostic code is not found, the ECM may have failed. Failure of the ECM is unlikely. Always contact the Technical Communicator at your dealership for possible consultation with Caterpillar prior