Inspection Procedure 5: Hunting (Repeated Acceleration and Deceleration) Occurs at the Set Vehicle Speed.


COMMENTS ON TROUBLE SYMPTOM




PROBABLE CAUSES



  • Malfunction of CAN bus system.
  • Malfunction of the ABS <vehicles without ASC>
  • Malfunction of the ASC <vehicles with ASC>
  • Malfunction of the diesel fuel 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 <Vehicles without ASC>.
Go to Step 3 <Vehicles with ASC>.
Repair the CAN bus lines (Refer to GROUP 54C - Troubleshooting, Can Bus Diagnostic Table ). Then go to Step 7.

STEP 2. Check the ABS diagnosis code <vehicles without ASC>.
Using M.U.T.-III, perform ABS diagnosis code (Refer to GROUP 35B - Diagnosis Function ).

Q. Is any diagnosis code set?
Repair the ABS (Refer to GROUP 35B - Troubleshooting, Diagnosis Code Chart ). Then go to Step 7.
Go to Step 4.

STEP 3. Check the ASC diagnosis <vehicles with ASC> code.
Using M.U.T.-III, perform ASC diagnosis code (Refer to GROUP 35C - Diagnosis Function ).

Q. Is any diagnosis code set?
Repair the ASC system (Refer to GROUP 35C - Troubleshooting, Diagnosis Code Chart ). Then go to Step 7.
Go to Step 4.

STEP 4. Check the diesel fuel system diagnosis code.
Using M.U.T.-III, perform diesel fuel system diagnosis code (Refer to GROUP 13A - Diagnosis Function ).

Q. Is any diagnosis code set?
Repair the diesel fuel system (Refer to GROUP 13A - Troubleshooting, Inspection Chart for Diagnosis Trouble Code ). Then go to Step 7.
Go to Step 5.

STEP 5. Check the data list.
Using M.U.T.-III, check the data list

  • Item 52: Vehicle speed signal
(Refer to data list reference table ) <BSY>.

Q. Is the check result normal?
Go to Step 6.
Replace the engine-ECU (Refer to GROUP 13A - Engine-ECU ). Then go to Step 7.

STEP 6. Retest the system

Q. Does a hunting occur?
Replace the engine-ECU (Refer to GROUP 13A - Engine-ECU ). Then go to Step 7.
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 7. Retest the system

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