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
    The following conditions are met for 3 seconds.

    • 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.

FAIL-SAFE AND BACKUP FUNCTION



  • The electrical continuity to the throttle valve control servo is discontinued.
  • The DPF regeneration is prohibited.
  • The EGR control is stopped (fully closed).
  • The AS&G control is prohibited.

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-12 throttle body assembly 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 throttle body assembly.

STEP 3. Connector check: B-10 engine-ECU connector

Q. Is the check result normal?
Go to Step 4 .
Repair or replace the connector.

STEP 4. Check harness between throttle body assembly connector and engine-ECU connector.

  1. Check the harness between B-12 (terminal No. 5) throttle body assembly connector and B-10 (terminal No. 129) engine-ECU connector.
  2. Check the harness between B-12 (terminal No. 6) throttle body assembly connector and B-10 (terminal No. 114) engine-ECU connector.
note Before checking harness, check intermediate connector A-17, and repair if necessary.

  • 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 throttle body assembly.

  • After replace the throttle body assembly, re-check the trouble symptoms.

Q. Does trouble symptom persist?
Replace the engine-ECU.
The check is end.