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. Connector check: B-12 electronic-controlled throttle valve connector

Q. Is the check result normal?
Go to Step 3 .
Repair or replace the connector.

STEP 3. Check throttle valve control servo itself.

  • Throttle valve control servo check (Refer to ).

Q. Is the check result normal?
Go to Step 4 .
Replace the throttle body assembly.

STEP 4. Connector check: B-26 engine-ECU connector


Q. Is the check result normal?
Go to Step 5 .
Repair or replace the connector.

STEP 5. Check harness between B-12 (terminal No. 1) electronic-controlled throttle valve connector and B-26 (terminal No. 15) engine-ECU connector.

  • Check output line for damage.

Q. Is the check result normal?
Go to Step 6 .
Repair the damaged harness wire.

STEP 6. Check harness between B-12 (terminal No. 2) electronic-controlled throttle valve connector and B-26 (terminal No. 16) engine-ECU connector.

  • Check output line for damage.

Q. Is the check result normal?
Go to Step 7 .
Repair the damaged harness wire.

STEP 7. 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 ).