0438995 JOHNSON CARBURETOR BODY ASSY., 150

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 the engine and check for an event code. If the event code is still active, temporarily replace the fuel filter differential pressure switch. Verify that the problem is resolved before permanently replacing the fuel filter differential pressure switch.STOP
Not OK - The event code is still active. There is an open circuit in the wiring for the fuel filter differential pressure switch between the connector for the fuel filter differential pressure switch and the ECM. There may be a problem with the ECM. Connect the connector for the pressure switch. Proceed to Test Step 3.Test Step 3. Check the ECM
Disconnect the J2/P2 ECM connector.
Fabricate a jumper wire that is long enough to create a short between the P2 ECM connector and the engine ground stud. Crimp a connector socket to one end of the jumper wire.
Remove the wire from terminal location P2-65 (fuel filter differential pressure switch) at the ECM connector. Install the jumper wire into the terminal location.
Secure the other end of the jumper wire to the engine ground stud.
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 problem is in the harness wiring between the connector for the fuel filter differential pressure switch and the P2 ECM connector. Check the harness connector to the fuel filter differential pressure switch for a good connection. Repair the connectors or wiring and/or replace the connectors or wiring. Verify that the repair eliminates the problem.STOP
Not OK - The event code is still active.Repair: There is a problem with the ECM. Replace the ECM. Refer to electronic troubleshooting Troubleshooting, "Replacing the ECM". Verify that the problem is resolved.STOP