Code No. P0657: Throttle Valve Control Servo Relay Circuit Malfunction

OPERATION

Battery voltage is applied to the throttle valve control servo relay terminal (terminal No. 4).
Battery voltage is applied to the throttle valve control servo relay terminal (terminal No. 2) from the engine control relay (terminal No. 2).
Engine-ECU (terminal No. 84) applies current to the throttle valve control servo relay coil by turning ON the power transistor in the unit in order to turn the relay ON.
When the throttle valve control servo relay turns ON, battery voltage is supplied by the throttle valve control servo relay (terminal No. 3) to the engine-ECU (terminal No. 72).

FUNCTION

When the ignition switch ON signal is input into the engine-ECU, the engine-ECU turns ON the throttle valve control servo.

TROUBLE JUDGMENT

Check Condition

Battery positive voltage is more than 8.3 V.

Judgement Criterion

The power line voltage of the electronic controlled throttle system is less than 6.0 V.

PROBALE CAUSES

Failed throttle valve return spring
Open/short circuit or harness damage in throttle valve control servo circuit or loose connector contact.
Failed engine-ECU

DIAGNOSIS

STEP 1. Connector check: A-21X throttle valve control servo relay connector

Q. Is the check result normal?

	Go to Step 2 .

	Repair or replace the connector.

STEP 2. Check throttle valve control servo relay itself.

Check throttle valve control servo relay itself (Refer to Throttle Valve Control Servo Relay Continuity Check ).

Q. Is the check result normal?

	Go to Step 3 .

	Repair.

STEP 3. Perform voltage measurement at A-21X throttle valve control servo relay connector.

Remove relay, and measure at relay box side.
Voltage between terminal No. 4 and earth.

OK: System voltage

Q. Is the check result normal?

	Go to Step 4 .

	Check and repair harness between A-21X (terminal No. 4) throttle valve control servo relay connector and battery. Check power supply line for open/short circuit.

STEP 4. Perform voltage measurement at A-21X throttle valve control servo relay connector.

Remove relay, and measure at relay box side.
Ignition switch: ON
Voltage between terminal No. 2 and earth.

OK: System voltage

Q. Is the check result normal?

	Go to Step 6 .

	Go to Step 5 .

STEP 5. Connector check: A-33X engine control relay connector

Q. Is the check result normal?

	Check and repair harness between A-33X (terminal No. 2) engine control relay connector and A-21X (terminal No. 2) throttle valve control servo relay connector. Check power supply line for open/short circuit.

	Repair or replace the connector.

STEP 6. Connector check: B-30 engine-ECU connector

Q. Is the check result normal?

	Go to Step 7 .

	Repair or replace the connector.

STEP 7. Perform voltage measurement at B-30 engine-ECU connector.

Disconnect connector, and measure at harness side.
Connect the terminal No. 73 of the engine-ECU harness connector to the earth.
Voltage between terminal No. 84 and earth.

OK: System voltage

Q. Is the check result normal?

	Go to Step 8 .

	Check and repair harness between A-21X (terminal No. 1) throttle valve control servo relay connector and B-30 (terminal No. 84) engine-ECU connector. Check earthing line for open/short circuit.

STEP 8. Perform voltage measurement at B-30 engine-ECU connector.

Disconnect connector, and measure at harness side.
Connect the terminals No. 72 and No. 84 of the engine-ECU harness connector to the earth.
Voltage between terminal No. 72 and earth.

OK: System voltage

Q. Is the check result normal?

	Go to Step 11 .

	Go to Step 9 .

STEP 9. Check harness between A-21X (terminal No. 3) throttle valve control servo relay connector and B-30 (terminal No. 72) engine-ECU connector.

Check output line for open/short circuit.

Q. Is the check result normal?

	Go to Step 10 .

	Repair the damaged harness wire.

STEP 10. Check harness between A-33X (terminal No. 2) engine control relay connector and A-21X (terminal No. 2) throttle valve control servo relay connector.

Check output line for damage.

Q. Is the check result normal?

	Check and repair harness between A-21X (terminal No. 1) throttle valve control servo relay connector and B-30 (terminal No. 84) engine-ECU connector. Check earthing line for open/short circuit.

	Repair the damaged harness wire.

STEP 11. Check harness between A-21X (terminal No. 4) throttle valve control servo relay connector and battery.

Check power supply line for damage.

Q. Is the harness connector in good condition?

	Go to Step 12 .

	Repair the damaged harness wire.

STEP 12. Check harness between A-21X (terminal No. 3) throttle valve control servo relay connector and B-30 (terminal No. 72) engine-ECU connector.

Check power supply line for damage.

Q. Is the harness connector in good condition?

	Go to Step 13 .

	Repair the damaged harness wire.

STEP 13. M.U.T.-III diagnosis code

Reconfirmation of diagnosis code.

Q. Is diagnosis code set?

	Replace the engine-ECU.

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