Code No. P0638: Throttle Valve Control Servo Circuit Range/Performance Problem

OPERATION

Refer to P2101 - Throttle Valve Control Servo Magneto Malfunction .

FUNCTION

Engine-ECU checks the electronic controlled throttle system for abnormal conditions.

TROUBLE JUDGMENT

Check Conditions

Battery positive voltage is more than 8.3 V.
Throttle position sensor (main) output voltage is more than 0.2 V and is less than 4.8 V.
Drop of throttle position sensor (main) output voltage per 100 milliseconds is more than 0.04 V.

Judgement Criterion

Throttle position sensor (main) output voltage is higher than the target throttle position sensor (main) voltage by 0.5 V or more.

Check Conditions

Battery positive voltage is more than 8.3 V.
Throttle position sensor (main) output voltage is more than 0.2 V and is less than 4.8 V.
Target throttle position sensor (main) output voltage is less than 1.5 V.

Judgement Criterion

Difference between throttle position sensor (main) output voltage and target throttle position sensor (main) voltage is more than 0.6 V.

Check Conditions

Battery positive voltage is more than 8.3 V.
Throttle position sensor (main) output voltage is more than 0.2 V and is less than 4.8 V.

Judgement Criterion

Difference between throttle position sensor (main) output voltage and target throttle position sensor (main) voltage is more than 1 V.

Check Condition

Battery positive voltage is more than 8.3 V.

Judgement Criterion

Throttle position sensor (main) default opening learnt value is more than 4 V.

PROBABLE CAUSES

Failed throttle valve return spring.
Failed throttle valve operation.
Failed throttle valve control servo.
Harness damage in throttle valve control servo circuit or loose connector contact.
Failed engine-ECU.

DIAGNOSIS

STEP 1. Check throttle body.

Check whether the throttle valve return spring is normal.

Q. Is the check result normal?

	Go to Step 2 .

	Replace the throttle body assembly.

STEP 2. Connector check: B-11 electronic-controlled throttle valve connector

Q. Is the check result normal?

	Go to Step 3 .

	Repair or replace the connector.

STEP 3. Check throttle valve control servo itself.

Check throttle valve control servo itself (Refer to ).

Q. Is the check result normal?

	Go to Step 4 .

	Replace the throttle body assembly.

STEP 4. Connector check: B-08 engine-ECU connector

Q. Is the check result normal?

	Go to Step 5 .

	Repair or replace the connector.

STEP 5. Check harness between B-11 (terminal No. 1) electronic-controlled throttle valve connector and B-08 (terminal No. 15) engine-ECU connector.

Check output line for damage.

Q. Is the check result normal?

	Go to Step 6 .

	Repair the damaged harness wire.

STEP 6. Check harness between B-11 (terminal No. 2) electronic-controlled throttle valve connector and B-08 (terminal No. 16) engine-ECU connector.

Check output line for damage.

Q. Is the check result normal?

	Go to Step 7 .

	Repair the damaged harness wire.

STEP 7. M.U.T.-III diagnosis code

Reconfirmation of diagnosis code.

Q. Is diagnosis code set?

	Replace engine-ECU.

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