STRIP 1604104 - Caterpillar

Transmission, SPN 127 FMI 4Conditions 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 4 means that the ECM has determined that the voltage of the circuit for the position sensor is below 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 above 4.95 DCV for more than two seconds, the ECM determines that the sensor is shorted to the + battery.The possible causes of this diagnostic code are listed below:
The signal circuit for the sensor is shorted to ground.
The sensor 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 4 is active before performing this procedure. Note: Use a digital multimeter for the measurements in this procedure.Test Step 1. CHECK THE SENSOR.
Turn the disconnect switch and the key start switch to the ON position.
Ensure that the diagnostic code is active.
Observe the status of the diagnostic code. Disconnect the sensor from the machine harness. Expected Result:The SPN 127 FMI 4 remains active. The FMI has not changed and the 4 is still active.Results:
OK - The diagnostic code remains active. The sensor is correct. Proceed to Test Step 2.
NOT OK - The diagnostic code is no longer active. The sensor has failed.Repair: Replace the sensor.STOPTest Step 2. CHECK THE WIRING HARNESS OF THE SENSOR FOR A SHORT TO GROUND.
Turn the key start switch and the disconnect switch to the OFF position.
Disconnect the machine harness from the sensor.
Disconnect the machine harness connector(s) from the ECM.
At the machine harness connector for the ECM, measure the resistance from the signal contact J1-51 of the machine harness to all possible sources of ground. Measure the resistance to all contacts of the machine harness connectors for the ECM. Expected Result:Each resistance measurement is greater than 5000 ohms.Results:
OK - Each resistance measurement is greater than 5000 ohms. The machine harness is correct. Proceed to Test Step 3.
NOT OK - One or more resistance measurements is not correct. There is a short in the machine harness. Repair: The short is between signal contact J1-51 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 IS STILL ACTIVE.
Inspect the harness connectors. Clean the contacts of the harness connectors and check the wires for damage to the insulation that is caused by excessive heat, battery acid, or chafing.
Perform a 45 N (10 lb) pull test on each of the wires that are associated with the circuit.
Reconnect all harness connectors in order