COVER 4T7862 - Caterpillar

Illustration 1 g03284856
Schematic of the transmission pump pressure sensorThis diagnostic code is related to the transmission oil pressure sensor. An FMI 03 means the Transmission ECM has determined that the signal output voltage of the pressure sensor is above normal.The sensor output is a Pulse Width Modulated (PWM) frequency signal at 500Hz ( 100Hz). The signal duty cycle changes as the sensor pressure changes.Possible causes for this diagnostic code are:
The sensor power supply may have failed.
The sensor may have failed.
The sensor output signal may be shorted to a voltage source.
The sensor output signal circuit may be open.
The Transmission ECM may have failed (unlikely).Note: The following test procedure may create other diagnostic codes. For now, ignore those codes. Clear those codes after the original diagnostic code has been corrected. Note: Poor connections are often the cause of a problem in electrical circuits. Before performing this procedure, inspect all of the harness connectors involved in the circuit. Verify that all of the connections in the circuit are clean, secure, and in good condition. If a problem is found with connections, correct the problem and verify that CID 0127 FMI 03 is still active before performing the following procedures. Test Step 1. VERIFY THE 24 VOLT SUPPLY.
Turn the key start switch and the disconnect switch to the ON position. Do not start the engine.
Do not disconnect any of the machine harness connectors at this time.
At the back of the harness connector for the transmission oil pressure sensor, insert the multimeter probes along contact A (171-GN), the sensor power supply and along contact B (C216-BK), the sensor GROUND.
Measure the voltage from contact A to contact B.Expected Result:The voltage measured is approximately 24 DCV.Results:
YES - The voltage measured is approximately 24 DCV. The power supply is correct. Go to Test Step 2.
NO - The voltage measurement is less than 24 DCV. The voltage is not correct. There is an open or loose connection in the circuit.Repair: There is a problem in the power supply circuit in the machine harness. Refer to the complete machine Electrical System Schematic. Check all of the connectors and the fuse in the 24V sensor supply circuit and the return circuit. Ensure that all connections are clean, secure, and in good condition. Repair or replace the machine harness as needed. To verify that the problem was corrected, and that the CID 0127 - FMI 03 diagnostic code is no longer active, go to Test Step 5.Test Step 2. CHECK THE SENSOR, THE ECM, AND THE CIRCUIT CONNECTIONS IN THE MACHINE HARNESS.
Turn the key start switch and the disconnect switch to the OFF position.
Disconnect the machine harness connector from the transmission oil pressure sensor.
At the harness connector for the transmission oil pressure sensor, place a jumper wire between contact E796-GN and contact C216-BK on the machine harness side of the connection.
Turn the key start switch and the disconnect switch to the ON position. Do not start the engine.
Observe the status of the diagnostic code.Expected Result:The CID 0127 FMI 03 diagnostic code