Inspection Procedure 20: Fuel Pump System

OPERATION

The fuel pump drive power is supplied from engine control relay to fuel pump relay (ETACS-ECU connector terminal F/PB) in the ETACS-ECU.
The battery voltage is applied by the ignition switch <Vehicles without KOS> or the OSS-ECU <Vehicles with KOS> to the fuel pump relay coil (ETACS-ECU connector terminal IG1) in the ETACS-ECU. The engine-ECU turns on the relay by turning ON the power transistor in the unit so as to conduct power to the fuel pump relay coil (via the ETACS-ECU connector terminal FP/R).
When the fuel pump relay is turned ON, the battery voltage will be supplied from the fuel pump relay (ETACS-ECU connector terminal F/PB) to the fuel pump connector terminal.

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 in the ETACS-ECU
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. Connector check: ETACS-ECU connectors

Q. Are the check results normal?

	Go to Step 2.

	Repair or replace the connector.

STEP 2. Check fuel pump relay.

Fuel pump relay continuity check (Refer to ).

Q. Is the check result normal?

	Go to Step 3.

	Replace the ETACS-ECU.

STEP 3. Perform voltage measurement at engine-ECU connector.

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

OK: System voltage

Q. Is the check result normal?

	Go to Step 4.

	Repair or replace the connector, or check and repair harness between engine-ECU connector terminal FP/R and ETACS-ECU connector terminal FP/R. Check power supply line for open/short circuit.

STEP 4. Perform voltage measurement at ETACS-ECU connector.

Disconnect connector, and measure at harness side.
Ignition switch: "ON"
Voltage between terminal F/PB and body earth.

OK: System voltage

Q. Is the check result normal?

	Go to Step 6.

	Go to Step 5.

STEP 5. Connector check: Engine control relay connector

Q. Is the check result normal?

	Check and repair harness between engine control relay connector terminal and ETACS-ECU connector terminal F/PB. Check power supply line for open/short circuit.

	Repair or replace the connector.

STEP 6. Check fuel pump operations.

Fuel pump connector check.
Fuel tank pump operation check (Refer to ).

Q. Is the check result normal?

	Go to Step 7.

	Repair or replace the connector, or replace the fuel tank pump and gauge assembly.

STEP 7. Perform resistance measurement at fuel pump connector.

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

OK: Continuity (2 Ω or less)

Q. Is the check result normal?

	Go to Step 8.

	Check and repair harness between fuel pump connector terminal earth line and body earth. Check earthing line for open circuit and damage.

STEP 8. Perform voltage measurement at fuel pump connector.

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

OK: System voltage

Q. Is the check result normal?

	Go to Step 10.

	Go to Step 9.

STEP 9. Check harness between ETACS-ECU connector terminal F/P and fuel pump connector.

Check power supply line for open/short circuit.

Q. Is the check result normal?

	Check and repair harness between engine-ECU connector terminal FP/R and ETACS-ECU connector terminal FP/R. Check power supply line for damage.

	Repair the damaged harness wire.

STEP 10. Check harness between engine control relay connector terminal and ETACS-ECU connector terminal F/PB.

Check power supply line for damage.

Q. Is the check result normal?

	Go to Step 11.

	Repair or replace the connector, or repair the damaged harness wire.

STEP 11. Check harness between ETACS-ECU connector terminal F/P and fuel pump connector terminal.

Check power supply line for damage.

Q. Is the check result normal?

	Go to Step 12.

	Repair the damaged harness wire.

STEP 12. 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.