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

OPERATION

Check code No. P2101: throttle valve control servo magneto malfunction (Refer to ).

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.

FAIL-SAFE AND BACKUP FUNCTION

Throttle opening degree position is in default position.

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 PROCEDURE

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. Check throttle valve control servo itself.

Electronic-controlled throttle valve control check.
Throttle valve control servo check (Refer to ).

Q. Is the check result normal?

	Go to Step 3.

	Repair or replace the connector, or replace the throttle body assembly.

STEP 3. Check harness between electronic-controlled throttle valve connector terminal and engine-ECU connector terminal ETV+.

Check signal line for damage.

Q. Is the check result normal?

	Go to Step 4.

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

STEP 4. Check harness between electronic-controlled throttle valve connector terminal and engine-ECU connector terminal ETV-.

Check output line for damage.

Q. Is the check result normal?

	Go to Step 5.

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

STEP 5. 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 ).