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

OPERATION

Battery voltage is applied to the throttle valve control servo relay connector terminal.
Battery voltage is applied to the throttle valve control servo relay terminal connector terminal from the engine control relay connector terminal.
Engine-ECU connector terminal C/RL 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 connector terminal to the engine-ECU connector terminal RSB.

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. Check throttle valve control servo relay itself.

Throttle valve control servo relay connector check.
Throttle valve control servo relay check (Refer to ).

Q. Is the check result normal?

	Go to Step 2.

	Repair or replace the connector, or replace the throttle valve control servo relay.

STEP 2. Perform voltage measurement at throttle valve control servo relay connector.

Remove relay, and measure at relay box side.
Voltage between terminal battery side power supply line and body earth.

OK: System voltage

Q. Is the check result normal?

	Go to Step 3.

	Repair or replace the connector, or check and repair harness between throttle valve control servo relay connector terminal and battery. Check power supply line for open/short circuit.

STEP 3. Perform voltage measurement at throttle valve control servo relay connector.

Remove relay, and measure at relay box side.
Ignition switch: ON
Voltage between terminal engine control relay side power supply line 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 control relay connector terminal and throttle valve control servo relay connector terminal. Check power supply line for open/short circuit.

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

Disconnect connector, and measure at harness side.
Short-circuit engine-ECU connector the terminal C/R to the body earth.
Voltage between terminal C/RL and body earth.

OK: System voltage

Q. Is the check result normal?

	Go to Step 5.

	Repair or replace the connector, or check and repair harness between throttle valve control servo relay connector terminal and engine-ECU connector terminal C/RL. Check earthing line for open/short circuit.

STEP 5. Perform voltage measurement at engine-ECU connector.

Disconnect connector, and measure at harness side.
Short-circuit engine-ECU connector terminals C/R and C/RL to the body earth.
Voltage between terminal RSB and body earth.

OK: System voltage

Q. Is the check result normal?

	Go to Step 8.

	Go to Step 6.

STEP 6. Check harness between throttle valve control servo relay connector terminal and engine-ECU connector terminal RSB.

Check output line for open/short circuit.

Q. Is the check result normal?

	Go to Step 7.

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

STEP 7. Check harness between engine control relay connector terminal and throttle valve control servo relay connector terminal.

Check power supply line for damage.

Q. Is the check result normal?

	Repair or replace the connector, or check and repair harness between throttle valve control servo relay connector terminal and engine-ECU connector terminal C/RL. Check earthing line for damage.

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

STEP 8. Check harness between throttle valve control servo relay connector terminal and battery.

Check power supply line for damage.

Q. Is the check result normal?

	Go to Step 9.

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

STEP 9. Check harness between throttle valve control servo relay connector terminal and engine-ECU connector terminal RSB.

Check output line for damage.

Q. Is the check result normal?

	Go to Step 10.

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

STEP 10. 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 ).