Inspection Procedure 9
Inspection Procedure 9: Hunting (Repeated Acceleration And Deceleration) Occurs At The Set Vehicle Speed [CVT.]COMMENT
- The secondary pulley speed sensor signal (vehicle speed signal) or the throttle body is suspected.
- The secondary pulley speed sensor signal (vehicle speed signal) is transmitted from the TCM to the ECM via CAN bus line.
NOTE: When the vehicle is driven with the low-speed gear in the sport mode, hunting occurs easily, however, this is not a failure.
TROUBLESHOOTING HINTS (THE MOST LIKELY CAUSES FOR THIS CASE:)
- Malfunction of the CAN bus line system.
- Malfunction of the CVT system.
- Malfunction of the MFI system.
- Malfunction of the secondary pulley speed sensor.
- Malfunction of the throttle body.
- Malfunction of the TCM.
- 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
CAUTION: If there is any problem in the CAN bus lines, an incorrect diagnostic trouble code (DTC) may be set. Prior to this diagnosis, diagnose the CAN bus lines (Refer to Trouble code diagnosis.) Scan Tool Testing and Procedures
STEP 1. Using scan tool MB991958, diagnose the CAN bus line.
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. Diagnose the CAN bus line. How to Diagnose the CAN Bus Line
Q: Is the check result satisfactory?
YES : Go to Step 2.
NO : Repair the CAN bus lines (Refer to Diagnosis - Can Bus Diagnostic Chart.) CAN Bus Diagnostics Table Then go to Step 6.
STEP 2. Using scan tool MB991958, check for CVT system DTC.
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 CVT system DTC (Refer to Diagnosis - Diagnostic Function.)
Q: Is any DTC set?
YES : Repair the CVT system (Refer to Diagnosis - Diagnostic Trouble Code Chart.) Diagnostic Trouble Code Descriptions Then go to Step 6.
NO : Go to Step 3.
STEP 3. Using scan tool MB991958, check for MFI system DTC.
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 6.
NO : Go to Step 4.
STEP 4. 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 5.
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 6.
STEP 5. 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 6.
NO : It can be assumed that this malfunction is intermittent.
STEP 6. Check the symptoms.
Q: Does hunting occur?
YES : Return to Step 1.
NO : The procedure is complete.