Inspection Procedure 7: Hunting (Repeated Acceleration and Deceleration) Occurs at the Set Vehicle Speed <4D5-A/T>.

OPERATION

The output shaft speed sensor signal (vehicle speed signal) is sent to the A/T-ECU. Engine-ECU receives the vehicle speed signal from the A/T-ECU via the CAN bus line.

COMMENTS ON TROUBLE SYMPTOM

The output shaft speed sensor circuit is suspected.
The CAN bus line between the engine-ECU and the A/T-ECU, the A/T-ECU, the engine-ECU may be defective.

note

When the vehicle is driven with the low-speed gear in the sport mode, hunting occurs easily, however, this is not a failure.

PROBABLE CAUSES

Malfunction of CAN bus system.
Damaged harness or connector.
Malfunction of the output shaft speed sensor.
Malfunction of the diesel fuel system.
Malfunction of the A/T system.
Malfunction of the A/T-ECU.
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 line 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 A/T system diagnosis code.

Using M.U.T.-III, perform A/T system diagnosis code (Refer to GROUP 23A - Troubleshooting, Diagnosis Function

Q. Is any diagnosis code set?

	Repair the A/T system (Refer to GROUP 23A - Troubleshooting, Diagnosis Code Chart ). Then go to Step 6.

	Go to Step 3.

STEP 3. Check the diesel fuel system diagnosis code.

Using M.U.T.-III, perform diesel fuel system diagnosis code (Refer to GROUP 13B <4D5> - Troubleshooting, Diagnosis Function

Q. Is any diagnosis code set?

	Repair the diesel fuel system. (Refer to GROUP 13B <4D5> - Troubleshooting, Inspection Chart for Diagnosis 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 13B <4D5> - Engine-ECU ). Then go to Step 6.

STEP 5. Check the symptom.

Q. Does a hunting occur?

	Replace the engine-ECU (Refer to GROUP 13B <4D5> - Engine-ECU ). 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. Check the symptom.

Q. Does a hunting occur?

	Return to Step 1.

	The procedure is complete.