RETAINER 4H8578 - Caterpillar

Chassis ECM
The following is a list of Diagnostic Trouble Codes (DTCs) that are associated with the analog passive sensors of the machine.
Table 1
Chassis ECM (MID 87)
DTC Code Description System Response
96-3 Fuel Level Sensor: Voltage above normal Fuel gauge indicator will report incorrectly.
96-4 Fuel Level Sensor: Voltage below normal Fuel gauge indicator will report incorrectly. Possible causes for an FMI 3 diagnostic code are:
The return circuit is open
The signal circuit is open or the sensor is disconnected.
The signal circuit is shorted to the +battery.
The sensor has failed.
The ECM has failed. A failure of the ECM is unlikely.Possible causes for an FMI 4 diagnostic code are:
The sensor has failed
The signal circuit for the sensor is shorted to ground
The ECM has failed. A failure of the ECM is unlikely.
Illustration 1 g03321149
Schematic of the Analog Passive Sensor
Note: The diagram above is a simplified schematic of the Chassis ECM and the Analog Passive Sensorconnections. The schematic is electrically correct. However, not all of the possible harness connectors are shown. Refer to the latest revision of Electrical Schematic, UENR1138 for the complete schematic.Diagnostic Trouble Code Procedure
Note: Prior to beginning this procedure, inspect the harness connectors that are involved in this circuit. Poor connections can often be the cause of a problem in an electrical circuit. Verify that all connections in the circuit are clean, secure, and in good condition. Check the wiring for pinch points or abrasions. Look for and repair areas that indicate wires are exposed. If a problem with a connection is found, correct the problem and verify that this diagnostic code is active before performing a troubleshooting procedure.
Table 2
Troubleshooting Test Steps Values Results
1. Identify Active FMI Code Associated With Sensor Circuit Code present FMI 3 diagnostic code, proceed to Test Step 2.
FMI 4 diagnostic code, proceed to Test Step 6.
Begin Process For FMI 3 Troubleshooting HERE
2. Check For An Open In The Return Circuit
A. Turn key start switch and disconnect switch OFF.
B. Disconnect the sensor from the machine harness.
C. At the machine harness for the sensor, measure the resistance from signal to frame ground.
The resistance is less than 5 Ω. OK - The resistance is less than 5 Ω.
Proceed to Test Step 3.
NOT OK- The resistance is greater than 5 Ω.
Repair: Repair or replace the machine harness.
Proceed to Test Step 8.
3. Check For An Open In The Signal Circuit
A. Turn key start switch and disconnect switch OFF.
B. Disconnect the machine harness J1 and J2 connectors from the ECM.
C. At the machine harness