Perform this procedure if you suspect that there is a problem in the circuit for the fuel filter differential pressure switch. The fuel filter differential pressure switch is used to monitor the differential pressure across the fuel filter element. The switch is normally closed. When the differential pressure at the switch reaches a trip point the switch will open. The Electronic Control Module (ECM) will alert the operator of fuel restriction. Use this test in order to verify that the fuel filter differential pressure switch is operating correctly.
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| Illustration 1 | g01378788 |
Schematic | |
Test Step 1. Inspect Electrical Connectors and Wiring
- Remove electrical power from the engine ECM.
- Thoroughly inspect connector (1). Also, thoroughly inspect the connector for switch (2) .
Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.
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| Illustration 2 | g01310457 |
Left side engine view (typical example) (1) J2/P2 ECM connectors | |
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| Illustration 3 | g01161069 |
Typical location of the fuel filter differential pressure switch (2) Fuel filter differential pressure 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.
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| Illustration 4 | g01378789 |
P2 ECM connector (P2-65) Fuel filter differential pressure switch (P2-83) Return for the switch | |
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| Illustration 5 | g01160725 |
Connector for the fuel filter differential pressure switch (Terminal 1) Fuel filter differential pressure switch (Terminal 2) Return for the switch | |
- 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 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.
STOP
Test 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 check indicates a short circuit.
Results:
- OK - The resistance check indicates a short circuit. The differential pressure switch is OK. Proceed to Test Step 3.
- 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.
STOP
Test Step 3. Check the Wiring between the Connector for the Differential Pressure Switch and the ECM
- Disconnect the J2/P2 ECM connector.
- Create a short 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.
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 next most likely cause of the problem is the differential pressure switch. The least likely cause of the problem is the ECM. The ECM can be tested by temporarily connecting a test ECM. Refer to Troubleshooting, "ECM - Replace".If the problem is resolved with the test ECM, install the suspect ECM. If the problem returns with the suspect ECM, replace the ECM. Verify that the problem is resolved.If the problem is not resolved with the test ECM, install the original ECM. There is a problem in the wiring.
STOP
- 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.
STOP