Inspection Procedure 10: Hunting (Repeated Acceleration and Deceleration) Occurs at the Set Vehicle Speed <4B11-Turbo>.


COMMENTS ON TROUBLE SYMPTOM



  • The wheel speed sensor signal (vehicle speed signal) or the throttle body is suspected.
  • The wheel speed sensor signal (vehicle speed signal) is transmitted from the ASC-ECU to the engine-ECU via the CAN bus line.

PROBABLE CAUSES



  • Malfunction of CAN bus system.
  • Malfunction of the ASC system
  • Malfunction of the throttle body.
  • Malfunction of the MPI system.
  • Malfunction of the engine-ECU.

DIAGNOSIS PROCEDURE
caution
  • If there is any problem in the CAN bus lines, an incorrect diagnosis code may be set. Prior to this diagnosis, diagnose the CAN bus lines.
  • Before replacing the ECU, ensure that the CAN bus lines is normal.

STEP 1. Check the CAN bus system diagnosis.
Using M.U.T.-III, perform CAN bus diagnosis (Refer to GROUP 54C - Explanation About The M.U.T-III Can Bus Diagnostics ).

Q. Is the check result satisfactory?
Go to Step 2.
Repair the CAN bus lines (Refer to GROUP 54C - Troubleshooting, Can Bus Diagnostic Table ). Then go to Step 6.

STEP 2. Check the ASC system diagnosis code.
Using M.U.T.-III, perform ASC system diagnosis code (GROUP 35C - Troubleshooting, Diagnostic Function ).

Q. Is any diagnosis code set?
Repair the ASC system (Refer to GROUP 35C - Troubleshooting, Diagnosis Code Chart ). Then go to Step 6.
Go to Step 3.

STEP 3. Check the MPI system diagnosis code.
Using M.U.T.-III, perform MPI system diagnosis code (Refer to GROUP 13C - Troubleshooting, Diagnosis Function ).

Q. Is any diagnosis code set?
Repair the MPI system (Refer to GROUP 13C - Troubleshooting, Inspection Chart for Diagnosis Trouble Code ). Then go to Step 6.
Go to Step 4.

STEP 4. Check the data list.
Using M.U.T.-III, check the data list (Refer to - data list reference table).

  • Item 04: Vehicle speed signal

Q. Is the check result normal?
Go to Step 5.
Replace the engine-ECU (Refer to GROUP 13C - Engine-ECU ). When the Engine-ECU is replaced, register the encrypted code (Refer to GROUP 42C - Troubleshooting, ID Code Registration Necessity Judgment Table ). Then go to Step 6.

STEP 5. Retest the system

Q. Does a hunting occur?
Replace the engine-ECU (Refer to GROUP 13C - Engine-ECU ). When the Engine-ECU is replaced, register the encrypted code (Refer to GROUP 42C - Troubleshooting, ID Code Registration Necessity Judgment Table ). Then go to Step 6.
It can be assumed that this malfunction is intermittent (Refer to GROUP 00 - How to Use Troubleshooting/Inspection Service Points, How to Cope with Intermittent Malfunction ).

STEP 6. Retest the system

Q. Does a hunting occur?
Return to Step 1.
The procedure is complete.