Inspection Procedure 8

Inspection Procedure 8: Hunting (Repeated Acceleration And Deceleration) Occurs At The Set Vehicle Speed [M/T.]

COMMENT
The vehicle speed sensor or the throttle body is suspected.

TROUBLESHOOTING HINTS (THE MOST LIKELY CAUSES FOR THIS CASE:)
- Malfunction of the MFI system.
- Malfunction of the vehicle speed sensor.
- Malfunction of the throttle body.
- Malfunction of the ECM.

DIAGNOSTIC PROCEDURE

Required Special Tools:
- MB991958: Scan Tool (M.U.T.-III Sub Assembly)
- MB991824: V.C.I.
- MB991827: M.U.T.-III USB Cable
- MB991910: M.U.T.-III Main Harness A

STEP 1. Using scan tool MB991958, check for MFI system DTC.







CAUTION: To prevent damage to scan tool MB991958, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991958.

1. Connect scan tool MB991958 to the data link connector. How to Connect the Scan Tool (M.U.T.-Iii.)
2. Turn the ignition switch to the "ON" position.
3. Check for MFI system DTC (Refer to MFI Diagnosis - Diagnostic Function.) Diagnostic Function

Q: Is any DTC set?

YES : Repair the MFI system (Refer to MFI Diagnosis - Diagnostic Trouble Code Chart.) Diagnostic Trouble Code Descriptions Then go to Step 4.

NO : Go to Step 2.

STEP 2. Using scan tool MB991958, check data list item 04: Vehicle speed.

1. Connect scan tool MB991958 to the data link connector. How to Connect the Scan Tool (M.U.T.-Iii.)
2. Turn the ignition switch to the "ON" position.
3. Set scan tool MB991958 to data reading mode for cruise control system. How to Connect the Scan Tool (M.U.T.-Iii.)
- Item 04: Vehicle speed.

Q: Is the check result satisfactory?

YES : Go to Step 3.

NO : Replace the ECM. When the ECM is replaced, register the encrypted code (Refer to Diagnosis - ID Code Registration Judgment Table.) ID Codes Registration Judgment Table Then go to Step 4.

STEP 3. Check the symptoms.

Q: Does hunting occur?

YES : Replace the ECM. When the ECM is replaced, register the encrypted code (Refer to Diagnosis - ID Code Registration Judgment Table.) ID Codes Registration Judgment Table Then go to Step 4.

NO : It can be assumed that this malfunction is intermittent.

STEP 4. Check the symptoms.

Q: Does hunting occur?

YES : Return to Step 1.

NO : The procedure is complete.