HANDLE AS 8T1785 - Caterpillar

System Operation Description: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 the table 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 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 2.
Table 2
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 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.
Illustration 1 g01379074
Schematic of the circuit that is for the fuel level sensor
Table 3
Troubleshooting Test Steps Values Results
1. Verify that the "Fuel Level Sensor Installation Status" Parameter is Programmed Correctly
A. Remove electrical power from the ECM.
B. Connect the Cat Electronic Technician (ET) to the service tool connector.
C. Restore electrical power to the ECM.
D. Establish communication with the ECM.
E. Verify that the "Fuel Level Sensor Installation Status" parameter is programmed to "Installed".
F. Remove electrical power from the ECM.
Parameter
Result: The "Fuel Level Sensor Installation Status" parameter is programmed correctly. Proceed to Test Step 2.
Result: The "Fuel Level Sensor Installation Status" parameter is programmed to "Not Installed".
Program the "Fuel Level Sensor Installation Status" parameter to " Installed". Verify that the repair eliminates the problem.
STOP
Illustration 2 g01379047
Location of the ECM connectors that are for the fuel level sensor (back engine view)
(1) J1/P1 ECM connectors
(2) Connector for the fuel level sensor
Illustration 3 g01379069
Terminal locations at the P1 ECM connectors that are associated with the fuel level sensor
(P1-15) Fuel level
(P1-3) Return
Illustration 4 g01155187
Connector for the fuel level sensor
(Terminal 1) Fuel level
(Terminal 2) Sensor return
Table 4
Troubleshooting Test Steps Values 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