Inspection Procedure 20: Fuel Pump System

OPERATION

The fuel pump drive power is supplied from engine control relay to fuel pump relay.
The battery voltage is applied by the ignition switch to the fuel pump relay coil. The engine-ECU connector terminal FP/R turns on the relay by turning ON the power transistor in the unit so as to conduct power to the fuel pump relay coil.
When the fuel pump relay is turned ON, the battery voltage will be supplied from the fuel pump relay to the fuel pump.

FUNCTION

When the ignition switch ON signal is inputted into the engine-ECU, the engine-ECU turns ON the fuel pump relay. This causes the battery voltage to be supplied to the fuel pump.

PROBABLE CAUSES

Failed fuel pump relay
Failed fuel pump
Open/short circuit or harness damage in fuel pump drive circuit, or loose connector contact.
Failed engine-ECU

DIAGNOSIS PROCEDURE

STEP 1. Check fuel pump relay.

Fuel pump relay continuity check (Refer to ).

Q. Is the check result normal?

	Go to Step 2.

	Replace the fuel pump relay.

STEP 2. Perform voltage measurement at engine-ECU connector.

Disconnect connector, and measure at harness side.
Ignition switch: ON
Voltage between terminal FP/R and earth.

OK: System voltage

Q. Is the check result normal?

	Go to Step 4.

	Go to Step 3.

STEP 3. Check of short to earth, open circuit in FP/R line between fuel pump relay connector and engine-ECU connector.

Q. Is the check result normal?

	Repair or replace the connector(s), or check and repair the harness of open circuit in coil power supply line between J/B connector terminal IG1 line and fuel pump relay connector terminal.

	Repair the connector(s) or wiring harness.

STEP 4. Perform voltage measurement at fuel pump relay connector.

Disconnect connector, and measure at harness side.
Ignition switch: ON
Voltage between terminal switch side power supply line and earth.

OK: System voltage

Q. Is the check result normal?

	Go to Step 5.

	Repair or replace the connector(s), or check and repair the harness of short to earth, and open circuit in power supply line between engine control relay connector and fuel pump relay connector.

STEP 5. Check fuel pump operations.

Fuel tank pump operation check (Refer to ).

Q. Is the check result normal?

	Go to Step 6.

	Replace the fuel tank pump and gauge assembly.

STEP 6. Perform resistance measurement at fuel pump connector.

Disconnect connector, and measure at harness side.
Resistance between terminal earth line and earth.

OK: Continuity (2 Ω or less)

Q. Is the check result normal?

	Go to Step 7.

	Repair or replace the connector(s), or check and repair the harness of open circuit and damage in earth line between fuel pump connector and body earth.

STEP 7. Check of open circuit, short circuit and damage in power supply line between fuel pump relay connector and fuel pump connector.

Q. Is the check result normal?

	Go to Step 8.

	Repair the connector(s) or wiring harness.

STEP 8. Check of damage in FP/R line between engine-ECU connector and fuel pump relay connector.

Q. Is the check result normal?

	Go to Step 9.

	Repair the connector(s) or wiring harness.

STEP 9. Check of damage in power supply line between engine control relay connector and fuel pump relay connector.

Q. Is the check result normal?

	Go to Step 10.

	Repair the connector(s) or wiring harness.

STEP 10. Check of damage in power supply line between J/B connector terminal IG1 line and fuel pump relay connector terminal.

Q. Is the check result normal?

	Go to Step 11.

	Repair the connector(s) or wiring harness.

STEP 11. M.U.T.-III actuator test

Item 9: Fuel pump

OK: Operating sound of fuel pump can be heard.

Q. Is the check result normal?

	Intermittent malfunction (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunctions ).

	Replace the engine-ECU.