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.

FAIL-SAFE AND BACKUP FUNCTION



  • Throttle opening degree position is in default position.

PROBABLE CAUSES



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

DIAGNOSIS PROCEDURE

STEP 1. Connector check: A-25X 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.

  • Throttle valve control servo relay continuity check (Refer to ).

Q. Is the check result normal?
Go to Step 3 .
Replace the throttle valve control servo relay.

STEP 3. Perform voltage measurement at A-25X 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-25X (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-25X 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-37X engine control relay connector

Q. Is the check result normal?

    Check and repair harness between A-37X (terminal No. 2) engine control relay connector and A-25X (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-27 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-27 engine-ECU connector.

  • Disconnect connector, and measure at harness side.
  • Short-circuit B-27 engine-ECU connector the terminal No. 73 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-25X (terminal No. 1) throttle valve control servo relay connector and B-27 (terminal No. 84) engine-ECU connector.

    • Check earthing line for open/short circuit.

STEP 8. Perform voltage measurement at B-27 engine-ECU connector.

  • Disconnect connector, and measure at harness side.
  • Short-circuit B-27 engine-ECU connector terminals No. 73 and No. 84 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-25X (terminal No. 3) throttle valve control servo relay connector and B-27 (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-37X (terminal No. 2) engine control relay connector and A-25X (terminal No. 2) throttle valve control servo relay connector.

  • Check power supply line for damage.

Q. Is the check result normal?

    Check and repair harness between A-25X (terminal No. 1) throttle valve control servo relay connector and B-27 (terminal No. 84) engine-ECU connector.

    • Check earthing line for damage.
Repair the damaged harness wire.

STEP 11. Check harness between A-25X (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-25X (terminal No. 3) throttle valve control servo relay connector and B-27 (terminal No. 72) engine-ECU connector.

  • Check output 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 ).