GUIDE AS 1445574 - Caterpillar

Transmission, SPN 127 FMI 3Conditions Which Generate This Code:
Illustration 1 g01338641
Connections of the transmission pressure sensor
This diagnostic code is associated with the transmission pressure sensor. The FMI 3 means that the ECM has determined that the voltage of the circuit for the sensor is above normal. The sensor monitors the hydraulic charge pressure.The output of the sensor is an analog signal from 0.2 DCV to 4.95 DCV. The voltage changes as the pressure changes. The ECM recognizes a voltage in the range of 0.2 DCV to 4.95 DCV as valid input from the sensor. If the voltage is below 0.2 DCV for more than two seconds, the ECM determines that the sensor is shorted to ground.The possible causes of this diagnostic code are listed below:
The signal circuit for the sensor is open.
The signal circuit for the sensor is shorted to the +battery circuit.
The sensor has failed.
The power circuit or the ground circuit has failed.
The ECM has failed. This is unlikely.Note: The following test procedure may create other diagnostic codes. Ignore these created diagnostic codes and clear the diagnostic codes when the original diagnostic code has been corrected. Ensure that the diagnostic code of SPN 127 FMI 3 is active before performing this procedure.Note: Use a digital multimeter for the measurements in this procedure.Test Step 1. CHECK FOR POWER AT THE SENSOR.
Do not disconnect the harness connector from the sensor.
Turn the key start switch and the disconnect switch to the ON position.
At the back of the harness connector for the sensor, insert a multimeter probe along the voltage supply wire (contact A).
Measure the voltage from contact A to frame ground. Expected Result:The voltage is +5 DCV.Results:
OK - The voltage is +5 DCV. Proceed to Test Step 2.
NOT OK - The voltage is not +5 DCV. The + battery circuit in the machine harness has failed.Repair: Replace the machine harness or repair the machine harness.STOPTest Step 2. CHECK FOR PROPER GROUND AT THE SENSOR.
The machine harness remains connected to the sensor.
Turn the key start switch and the disconnect switch to the OFF position.
Remove the multimeter probe from the voltage supply wire (contact A).
At the back of the harness connector for the sensor, insert a multimeter probe along the ground wire (contact B).
Measure the resistance from contact B to frame ground. Expected Result:The resistance is less than 5 ohms.Results:
OK - The resistance is less than 5 ohms. The ground circuit is correct. Proceed to Test Step 3.
NOT OK - The resistance is greater than 5 ohms. The ground circuit in the machine harness has failed.Repair: Replace the machine harness or repair the machine harness.STOPTest Step 3. CHECK THE WIRING HARNESS OF THE SENSOR FOR AN OPEN CIRCUIT.
The key start switch and the disconnect switch remain in the OFF position.
Disconnect the machine harness from the sensor.
At the harness connector for the sensor, connect a jumper wire between contact B and contact C.
Disconnect the machine harness connector(s) from the ECM.
At the harness connector for the ECM, measure the resistance between contact J1-12 and contact