COVER 8M9343 - 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 Derate
E390-3 Fuel Filter Restriction ShutdownThe 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 g01214403
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 g01214409
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 the correct torque value.
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 at the Harness Connector
Fabricate a jumper wire that is long enough to short circuit the terminals at the harness connector for the fuel filter differential pressure switch. Crimp connector pins to each end of the jumper wire.
Disconnect the connector for the fuel filter differential pressure switch from the harness. Install the jumper wire across the terminals on the harness side of this connector.
Start the engine. Increase the engine speed to high idle.
Check for an event code for the engine fuel filter restriction.
Shut down the engine. Remove electrical power from the ECM. Expected Result:The event code is not active.Results:
OK - The event code is not active.Repair: The wiring between the connector and the ECM is OK. Replace the fuel filter element. Restart