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

OPERATION

The electric current from the engine-ECU <M/T> or engine-A/T-ECU <A/T> (terminal No. 133 and No. 141) to the throttle valve control servo (terminal No. 1 and No. 2) is controlled.

FUNCTION

engine-ECU <M/T> or engine-A/T-ECU <A/T> checks the electronic-controlled throttle system for abnormal conditions.

TROUBLE JUDGMENT

Check Conditions

Battery positive voltage is 8.3 V or more.
Ignition switch is in ON position.

Judgement Criteria

The drive current of the throttle valve control servo is not normal.

or

The temperature in the drive circuit of the throttle valve control servo is not normal.

Check Conditions

Ignition switch is in ON position.
Throttle position sensor (main) is normal.

Judgement Criterion

Throttle position sensor (main) mid opening learning value is 4.0 V or more.

PROBABLE CAUSE

Failed throttle valve return spring.
Failed throttle valve operation.
Failed throttle valve control servo.
Open/short circuit in throttle valve control servo circuit or loose connector contact.
Failed engine-ECU <M/T>.
Failed engine-A/T-ECU <A/T>.

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 throttle body assembly.

STEP 2. Check throttle valve control servo relay itself.

Check throttle valve control servo (Refer to ).

Q. Is the check result normal?

	Go to Step 3 .

	Replace throttle body assembly.

STEP 3. Connector check: B-06 electronic-controlled throttle valve connector

Q. Is the check result normal?

Go to Step 4 .

Repair or replace.

STEP 4. Connector check: C-114 engine-ECU <M/T> or engine-A/T-ECU <A/T> connector

Q. Is the check result normal?

Go to Step 5 .

Repair or replace.

STEP 5. Check harness between B-06 (terminal No. 2) electronic-controlled throttle valve connector and C-114 (terminal No. 141) engine-ECU <M/T> or engine-A/T-ECU <A/T> connector.

Check output line for short circuit and damage.

Q. Is the check result normal?

Go to Step 6 .

Repair.

STEP 6. Check harness between B-06 (terminal No. 1) electronic-controlled throttle valve connector and C-114 (terminal No. 133) engine-ECU <M/T> or engine-A/T-ECU <A/T> connector.

Check output line for short circuit and damage.

Q. Is the check result normal?

Go to Step 7 .

Repair.

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

Reconfirmation of diagnosis code.

Q. Is the diagnosis code set?

	Replace engine-ECU <M/T> or engine-A/T-ECU <A/T>.

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