Code No. P0638: Throttle Valve Control Servo Stuck


OPERATION



  • The electric current from the engine-ECU connector terminal ETV- and ETV+ to the throttle valve control servo connector terminal 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. Check throttle valve control servo itself.

  • Throttle body assembly connector check.
  • Check throttle valve control servo itself (Refer to ).

Q. Is the check result normal?
Go to Step 2.
Repair or replace the connector, or replace the throttle body assembly.

STEP 2. Check harness between throttle body assembly connector and engine-ECU connector.

  1. Check the harness between throttle body assembly connector terminal and engine-ECU connector terminal ETV-.
  2. Check the harness between throttle body assembly connector terminal and engine-ECU connector terminal ETV+.

  • Check output line for open/short circuit and damage.

Q. Are the check results normal?
Go to Step 3.
Repair or replace the connector, or repair the damaged harness wire.

STEP 3. 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.