STUD 6H0192 - Caterpillar

System Operation Description:The fuel level sensor is an OEM installed component for the vessel. The sensor is a passive sensor. The sensor does not require an operating voltage from the Electronic Control Module (ECM).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 sensor's variable resistance affects the pull-up voltage that is created by the ECM. When the sensor's resistance is low, the pull-up voltage is low. When the sensor's resistance is high, the pull-up voltage is high. Refer to Table 1.
Table 1
Relationship Between the Sensor's Resistance 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    If the voltage on the signal wire falls below 0.15 VDC, a 96-04 diagnostic code is activated. If the voltage on the signal wire rises above 1.8 VDC, a 96-03 diagnostic code is activated. There is an eight second delay before either code is activated.A diagnostic code is probably caused by a problem in a wiring harness. The next likely cause is a problem with the fuel level sensor. The least likely cause is a problem with the ECM.
Illustration 1 g01129074
Schematic for the fuel level sensorTest Step 1. Inspect the Electrical Connectors and the Wiring
Turn the keyswitch to the OFF position.
Illustration 2 g01130312
Engine components for the fuel level sensor (1) J1/P1 ECM connectors (2) J803/P803 connectors for the fuel level sensor
Thoroughly inspect connectors (1) and (2). Refer to Troubleshooting, "Electrical Connectors-Inspect" for details.
Illustration 3 g01130327
P1 terminals that are associated with the fuel level sensor (P1-3) Return (P1-15) Signal
Illustration 4 g01120369
Harness connector for the fuel level sensor (1) Signal (2) Return
Perform a 45 N (10 lb) pull test on each of the wires that are associated with the fuel level sensor.
Check the allen head screw on the ECM connectors for the proper torque. Refer to Troubleshooting, "Electrical Connectors - Inspect" for the correct torque values.
Check the harness and the wiring for abrasion and for pinch points from the fuel level sensor to the ECM.Expected Result:All connectors, pins and sockets are completely coupled and/or inserted and the harness and wiring are free of corrosion, of abrasion and of pinch points.Results:
OK - The connectors and the wiring are OK. Proceed to Test Step 2.
Not OK - There is a problem in the connectors and/or the wiring.Repair: Repair the connectors and/or the wiring. Replace parts, if necessary. Verify that the repair eliminates the problem.STOPTest Step 2. Check for Active Diagnostic Codes
Connect the Caterpillar Electronic Technician (ET) to the service tool connector. Refer to Troubleshooting, "Electronic Service Tools".
Turn the keyswitch to the ON position.
Observe the "Active Diagnostic" screen on Cat ET. Wait at least 15 seconds so that any codes may become active. Look