Auxiliary Fuel Pump Checking

Auxiliary Fuel Pump Checking

Special tools, testers and auxiliary items required

• Multimeter.

• Electrical connector test lead set.

Test conditions

• Battery voltage 12.5 V.

• Fuse 27 in Fuse Panel C is OK.

• Fuel filter OK.

• Ignition switched off.

Test procedure

- Perform a preliminary check to verify the customers complaint. Refer to => [ Preliminary Check ] Preliminary Check

Start diagnosis

- Disconnect the electrical harness connector from the Auxiliary Fuel Pump (V393) (right side of engine. See Repair Information, auxiliary fuel pump removal for location).

- Connect a multimeter to both terminals of the Auxiliary Fuel Pump (V393) connector and check the motor resistance.

Specified value: 1.4 Ohm (+/-.5 ohm).

- If the Specified value was Not obtained, replace the Auxiliary Fuel Pump (V393)

- If the Specified value was obtained:

- Remove the Fuel Pump Relay (J49) (under dash, left side. Refer to component location in wiring diagrams.)

- Turn the ignition ON.

- Using a test lamp connected to ground, touch terminal 30 of the Fuel Pump Relay (J49).

The test lamp should be ON.

- Using a test lamp connected to ground, touch terminal 86 of the Fuel Pump Relay (J49).

The test lamp should be ON.

If the test lamp was Not ON for any above test:

- Check the circuit between the Fuel Pump Relay (J49) terminal 30 to fuse 27 in Fuse Box C, or Fuel Pump Relay (J49) terminal 86 to fuse 15 in Fuse Box B for an open, short to ground or high resistance. Refer to Wiring Diagrams for fuse locations.

If the test lamp was ON for both tests:

- Turn the ignition OFF.

- Install a jumper from relay terminal 30 to relay terminal 87.

- Turn the ignition ON.

The Auxiliary Fuel Pump (V393) should operate.

- If the Auxiliary Fuel Pump (V393) does operate:

- Replace the Fuel Pump Relay (J49) and retest for operation.

- If the Auxiliary Fuel Pump (V393) still does Not operate:

- Remove the Engine Control Module (ECM) (J623). Refer to the Repair Information for removal instructions.

- Check the resistance of the circuit from relay terminal 85 to the Engine Control Module (ECM) (J623) T60/15 terminal.

Specified value: 1.5 Ohm or less.

- If the specified value was not obtained, repair the circuit between the relay and the ECM for an open, high resistance or short. Refer to Wiring Diagrams for circuit locations.

- If the specified value was obtained, replace the Engine Control Module (ECM) (J623). Refer to the Repair Information for removal instructions.

- If the Auxiliary Fuel Pump (V393) did Not operate with the jumper connected:

- Leave ignition ON and jumper connected.

- Connect a test lamp to ground and touch terminal 2 of the Auxiliary Fuel Pump (V393) electrical harness connector.

The test lamp should be ON.

- If the test lamp is Not ON, check for an open circuit between the relay terminal 87 and the Auxiliary Fuel Pump (V393) harness connector terminal 2 for an open or high resistance. Repair as necessary. Refer to Wiring Diagrams for circuit locations.

- If the test lamp is ON, remove the test lamp from engine ground and connect it to terminal 1 of the Auxiliary Fuel Pump (V393) connector. Touch the other end of the test lamp to terminal 2.

- The test lamp should be ON.

- If the test lamp is Not ON, check for an open circuit between the Auxiliary Fuel Pump (V393) harness connector terminal 1 to ground for an open or high resistance. Repair as necessary. Refer to Wiring Diagrams for circuit locations.

- If the test lamp was ON, replace the Auxiliary Fuel Pump (V393).

Final procedures

After the repair work, the following work steps must be performed in the following sequence:

1. Check the DTC memory. Refer to => [ Diagnostic Mode 03 - Read DTC Memory ] Diagnostic Modes 01 - 09.

2. If necessary, erase the DTC memory. Refer to => [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Modes 01 - 09.

3. If the DTC memory was erased, generate readiness code. Refer to => [ Readiness Code ] Monitors, Trips, Drive Cycles and Readiness Codes.