SEAL-PIN 2299323 - Caterpillar

The fuel level sensor is a component that is installed by the customer. The sensor is a passive sensor. The sensor does not require an operating voltage from the Electronic Control Module (ECM).Use this procedure to troubleshoot the electrical system if a problem is suspected with the fuel level sensor or if any one of the diagnostic codes in Table 1 is active or easily repeated.
Table 1
Diagnostic Codes Table    
Code and Description    Conditions which Generate this Code    System Response    
96-3 Fuel Level Sensor voltage above normal     The voltage on the signal wire for the fuel level sensor is above normal.     The code is logged.    
96-4 Fuel Level Sensor voltage below normal     The voltage on the signal wire for the fuel level sensor is below normal.    When the fuel tank is full, the fuel level sensor has a resistance of 33 Ohms. When the fuel tank is empty, the fuel level sensor has a resistance of 240 Ohms. The resistance from the fuel level sensor varies between these values as the fuel level varies.The variable resistance of the sensor affects the pull-up voltage that is created by the ECM. When the resistance of the sensor is low, the pull-up voltage is low. When the resistance of the sensor is high, the pull-up voltage is high. Refer to Table 2.
Table 2
Relationship Between the Resistance of the Sensor and the Voltage on the Signal Wire    
Fuel Level     Resistance     Approximate Voltage on the Signal Wire    
Full     33 Ohms     0.15 VDC    
Empty     240 Ohms     1.8 VDC    The most likely electrical problem with the circuit for the fuel level sensor is a problem in the wiring harness. The next likely cause is a problem with the fuel level sensor. The least likely cause is a problem with the ECM.
Table 3
Troubleshooting Test Steps     Expected Results     Results    
2. Inspect the Electrical Connectors and the Wiring
A. Remove the electrical power from the ECM.
B. Thoroughly inspect connectors (1) and (2) . Refer to Troubleshooting, "Electrical Connectors-Inspect" for details.
C. Perform a 45 N (10 lb) pull test on each of the wires that are associated with the fuel level sensor.
D. Check the allen head screw on each of the ECM connectors for the proper torque. Refer to Troubleshooting, "Electrical Connectors - Inspect" for the correct torque values.
E. Check the harness and the wiring for abrasion and for pinch points from the fuel level sensor to the ECM.    
All connectors, pins, and sockets are coupled and/or inserted and the harness and wiring are free of corrosion, of abrasion and of pinch points.
   
Result: The connectors and the wiring are OK.
Proceed to Test Step 3.
Result: There is a problem in the connectors and/or the wiring.
Repair the connectors and/or the wiring. Replace parts, if necessary. Verify that the repair eliminates the problem.    
3. Check the Resistance of the Sensor at the Harness Connector
A. Disconnect the fuel