F7048 Force STOP NUT

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Schematic
Test Step 1. Inspect Electrical Connectors and Wiring
Turn the keyswitch to the OFF position.
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Left side engine view (typical example)
(1) J2/P2 ECM connectors
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Typical location of the fuel filter differential pressure switch
(2) Fuel filter differential pressure switch
Thoroughly inspect connector (1). Also, thoroughly inspect the connector for switch (2). Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.
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P2 ECM connector
(P2-65) Fuel filter differential pressure switch
(P2-83) Return for the switch
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Connector for the fuel filter differential pressure switch
(Terminal 1) Fuel filter differential pressure switch
(Terminal 2) Return for the switch
Perform a 45 N (10 lb) pull test on each of the wires in the ECM connector and the sensor connectors that are associated with the active diagnostic code.
Check the ECM connector (allen head screw) for the proper torque. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.
Check the harness and wiring for abrasions and for pinch points from the sensors back to the ECM. Expected Result:All connectors, pins, and sockets are completely coupled and/or inserted. The harness and wiring are free of corrosion, of abrasion, and of pinch points.Results:
OK - The harness and wiring are OK. Proceed to Test Step 3.
Not OK - There is a problem in the connectors and/or wiring.Repair: Repair the connectors or wiring and/or replace the connectors or wiring. Ensure that all of the seals are properly in place and ensure that the connectors are completely coupled.Verify that the repair eliminates the problem.STOPTest Step 2. Check the Switch Circuit with no Pressure in the Fuel System
Disconnect the connector for the differential pressure switch.
Check continuity between the terminals for the differential pressure switch at the connector. Expected Result:The resistance check indicates a short circuit.Results:
OK - The resistance check indicates a short circuit. Proceed to Test Step 3.
Not OK - The resistance check indicates an open circuit. There is an open circuit in the fuel filter differential pressure switch.Repair: Replace the differential pressure switch.STOPTest Step 3. Check the Switch Circuit with Pressure in the Fuel System
Turn the keyswitch to the ON position. Note: The fuel priming pump will run for two minutes.
While the fuel priming pump is running, check continuity between the terminals for the differential pressure switch at the connector.
Turn the keyswitch to the OFF position. Expected Result:The resistance check indicates a short circuit.Results:
OK - The resistance check indicates a short circuit. The differential pressure switch is OK. Proceed to Test Step 4.
Not OK - The resistance check indicates an open circuit. There is an open circuit in the wiring for the fuel filter differential pressure switch.Repair: Replace the differential pressure switch.STOPTest Step 4. Check for an Open in the Wiring between the Connector for the Differential Pressure Switch and the ECM
Disconnect the J2/P2 ECM connector.
Create a short on the ECM side of the harness between the terminals of the connector for the differential pressure switch.
Check continuity at the ECM connector between terminal P2-65 (fuel filter pressure switch) and terminal P2-83 (switch return). Expected Result:The resistance check indicates a short circuit.Results:
OK - The resistance check indicates a short circuit. Proceed to Test Step 5.
Not OK - The resistance check indicates an open circuit.Repair: Repair the connectors or wiring and/or replace the connectors or wiring between the ECM and the connector for the differential pressure switch.STOPTest Step 5. Check for a Short in the Wiring between the Connector for the Differential Pressure Switch and the ECM
Check continuity at the ECM connector between terminal P2-65 (fuel filter pressure switch) and every terminal on the P1 and P2 ECM connectors. Expected Result:The resistance checks indicate an open circuit.Results:
OK - The resistance checks indicate an open circuit.Repair: Check all connectors and wiring. Ensure that there are clean, solid connections at each connector. Return all wiring to the original configuration and retest the circuit. The most likely cause of the problem is a poor connection. The ECM can be tested by removing the wire P2-65 (fuel filter pressure switch) from the P1 ECM connector. Start and run the engine. After an hour, check for a E390 event code. If the event code is activated with the open in place at the ECM connector, replace the ECM. Refer to Troubleshooting, "ECM - Replace". Verify that the problem is resolved.STOP
Not OK - The resistance checks indicate a short circuit.Repair: Repair the connectors or wiring and/or replace the connectors or wiring between the ECM and the connector for the differential pressure switch.STOP