Inspection Procedure 5
Inspection Procedure 5: Hunting (Repeated Acceleration and Deceleration) Occurs at the Set Vehicle Speed.COMMENT
The output shaft speed sensor signal or the throttle body is suspected.
TROUBLESHOOTING HINTS (The most likely causes for this case:)
Malfunction of the CAN bus line system.
Malfunction of the output shaft speed sensor.
Malfunction of the throttle body.
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, 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.
2. Turn the ignition switch to the "ON" position.
3. Diagnose the CAN bus line.
4. Turn the ignition switch to the "LOCK" (OFF) position.
5. Disconnect scan tool MB991958.
Q: Is the check result satisfactory?
YES: Go to Step 2
NO: Repair the CAN bus lines (Refer to Diagnosis - CAN Bus Diagnostics Chart). Then go to Step 5.
STEP 2. Using scan tool MB991958, read the A/T system diagnostic trouble code.
1. Connect scan tool MB991958 to the data link connector.
2. Turn the ignition switch to the "ON" position.
3. Check for A/T system diagnostic trouble code (Refer to Automatic Transaxle Diagnosis - Diagnostic Function - How to Read and Erase Diagnostic Trouble Codes).
4. Turn the ignition switch to the "LOCK" (OFF) position.
5. Disconnect scan tool MB991958.
Q: Is DTC P0720 set?
YES: Refer to Automatic Transaxle Diagnosis - Diagnostic Trouble Code Procedures - DTC P0720: Output Shaft Speed Sensor System. Then go to Step 5.
NO: Go to Step 3.
STEP 3. Using scan tool MB991958, read the MFI system diagnostic trouble code.
1. Connect scan tool MB991958 to the data link connector.
2. Turn the ignition switch to the "ON" position.
3. Check for MFI system diagnostic trouble code (Refer to Diagnostic Function - How to Read and Erase Diagnostic Trouble Codes). Reading Diagnostic Trouble Codes
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 Diagnostic Trouble Code Chart). Then go to Step 5. Diagnostic Trouble Code Descriptions
NO: Go to Step 4.
STEP 4. Retest the system
Q: Does hunting occur?
YES: Replace the ECM. When the ECM is replaced, register the encrypted code (Refer to Diagnosis - ID Code Registration Necessity Judgment Table). Then go to Step 5.
NO: It can be assumed that this malfunction is intermittent.
STEP 5. Retest the system
Q: Does hunting occur?
YES: Return to Step 1.
NO: The procedure is complete.