Code No. P0638: Throttle Valve Control Servo Stuck

OPERATION

The electric current from the engine- ECU (terminal No. 129 and No. 114) to the throttle valve control servo (terminal No. 5 and No. 6) is controlled.

FUNCTION

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

TROUBLE JUDGMENT

Check Conditions

Battery positive voltage is 6 - 16 V
2 seconds later after the ignition switch has been in "ON" position
The engine static state

Judgment Criterion

The difference between the objective and real openings is 5° or more.

PROBABLE CAUSES

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

DIAGNOSIS PROCEDURE

STEP 1. Connector check: B-31 electronic-controlled throttle valve connector

Q. Is the check result normal?

	Go to Step 2 .

	Repair or replace the connector.

STEP 2. Check throttle valve control servo itself.

Check throttle valve control servo itself (Refer to ).

Q. Is the check result normal?

	Go to Step 3 .

	Replace the electronic-controlled throttle valve.

STEP 3. Connector check: D-215 engine-ECU connector

Q. Is the check result normal?

	Go to Step 4 .

	Repair or replace the connector.

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

Check the harness between B-31 (terminal No. 5) electronic-controlled throttle valve connector and D-215 (terminal No. 129) engine-ECU connector.
Check the harness between B-31 (terminal No. 6) electronic-controlled throttle valve connector and D-215 (terminal No. 114) engine-ECU connector.

Check output line for open/short circuit and damage.

Q. Are the check results normal?

	Go to Step 5 .

	Repair the damaged harness wire.

STEP 5. Replace the electronic-controlled throttle valve assembly.

After replace the electronic-controlled throttle valve assembly, re-check the trouble symptoms.

Q. Does trouble symptom persist?

Replace the engine-ECU. When the engine-ECU is replaced, write the chassis number (Refer to GROUP 00 - Precautions Before Service - How to Perform Chassis Number Writing

). After replacing the engine-ECU, register the injector identification code and learn fuel injection (Refer to GROUP 00 - Precautions Before Service - What The Common Rail Engine Learns

). After registering the injector identification code, the vehicle equipped with the closed type DPF carries out the forcible DPF regeneration. (Refer to GROUP 17 - Diesel Particulate Filter (DPF) System - Forcible DPF Regeneration

	The check is end.