Inspection Procedure 6

INSPECTION PROCEDURE 6: Hunting (Repeated Acceleration and Deceleration) Occurs at the Set Vehicle Speed .

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

TROUBLESHOOTING HINTS (The most likely causes for this case:)
- Malfunction of the vehicle speed sensor.
- Malfunction of the throttle body.
- Malfunction of the MFI system
- Malfunction of the ECM.

DIAGNOSIS

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 diagnostic trouble code.






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. Scan Tool Connecting
2. Turn the ignition switch to the "ON" position.
3. Check for MFI system diagnostic trouble code (Refer to MFI, Diagnosis - Diagnostic Function). Diagnostic Trouble Code Descriptions
4. Turn the ignition switch to the "LOCK" (OFF) position.
5. Disconnect scan tool MB991958.

Q: Is any DTC set?

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

NO : Go to Step 2.

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

1. Connect scan tool MB991958 to the data link connector. Scan Tool Connecting
2. Turn the ignition switch to the "ON" position.
3. Set scan tool MB991958 to data reading mode for auto-cruise control system. Reading Diagnostic Trouble Codes
- Item 04: Vehicle speed sensor.

4. Turn the ignition switch to the "LOCK" (OFF) position.
5. Disconnect scan tool MB991958.

Q: Is the vehicle speed sensor operating properly?

YES : Go to Step 3.

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

STEP 3. Retest the system

Q: Does hunting occur?

YES : Replace the ECM. When the ECM is replaced, register the encrypted code (Refer to Wireless Control Module, Troubleshooting - ID Code Registration Necessity Judgment Table). Then go to Step 4.

NO : It can be assumed that this malfunction is intermittent (Refer to General (Body and Chassis), How to Use Troubleshooting/Inspection Service Points - How to Cope with Intermittent Malfunction).

STEP 4. Retest the system

Q: Does hunting occur?

YES : Return to Step 1.

NO : The procedure is complete.