SHEET AS 3073303 - Caterpillar

Perform this procedure if you suspect that there is a problem in the circuit for the fuel filter differential pressure switch.This procedure covers the following event codes:
E390-1 Fuel Filter Restriction Warning
E390-2 Fuel Filter Restriction DerateThe fuel filter differential pressure switch is used to detect excessive restriction in the fuel filter. The switch is normally closed. When the fuel pressure at the switch reaches 103 14 kPa (15 2 psi) the switch will open. The switch is used in order to detect a plugged fuel filter element. The Electronic Control Module (ECM) will alert the operator of the condition. Use this test in order to verify that the fuel filter differential pressure switch is operating correctly.
Illustration 1 g01322152
Schematic for fuel filter differential pressure switch
Test Step 1. Inspect the Electrical Connectors and the Wiring
Remove electrical power from the ECM.
Illustration 2 g01214446
Left side engine view (typical example)
(1) J2/P2 ECM connectors
Illustration 3 g01161069
Fuel filter base (typical example)
(2) Fuel filter differential pressure switch
Thoroughly inspect connectors (1). Also, thoroughly inspect each connector for switch (2). Refer to the diagnostic functional test Troubleshooting, "Electrical Connectors - Inspect" for details.
Illustration 4 g01321577
P2 ECM connector
(P2-65) Fuel filter differential pressure switch
(P2-83) Signal return
Illustration 5 g01155187
Connector for the fuel filter differential pressure switch
(Terminal 1) Fuel filter differential pressure switch
(Terminal 2) Signal return
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 allen head screw of each ECM connector for the proper torque. Refer to the diagnostic functional test Troubleshooting, "Electrical Connectors - Inspect" for details.
Check the harness and wiring for abrasions and for pinch points from the switch 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 appear to be OK. Proceed to Test Step 2.
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
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