M/T
Hunting (Repeated Acceleration and Deceleration) Occurs at the Set Vehicle SpeedCOMMENT
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 ECM.
DIAGNOSIS
Required Special Tools:
- MB991958: Scan Tool (MUT-III Sub Assembly)
- MB991824: V.C.I.
- MB991827: MUT-III USB Cable
- MB991911: MUT-III Main Harness B
- MB992006: Extra Fine Probe
STEP 1. Using scan tool MB991958, read the 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.
2. Turn the ignition switch to the "ON" position.
3. Check for MFI system diagnostic trouble code (Refer to MFI Diagnosis - How to Read and Erase Diagnostic Trouble Code.) How to Read and Erase Diagnostic Trouble Code.
4. Turn the ignition switch to the "LOCK" (OFF) position.
5. Disconnect scan tool MB991958.
Q: Is any DTC set?
YES: Repair the MFI control 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. Check the vehicle speed sensor.
1. Remove the vehicle speed sensor and connect a 3 - 10-kohm resistor as shown in the illustration.
2. Turn the shaft of the vehicle speed sensor and check that there is voltage between terminals 2 - 3. (one turn = four pulses)
Q: Is the voltage within specifications?
YES: Go to Step 3.
NO: Replace the vehicle speed sensor. Then go to Step 4.
STEP 3. Retest the system
Q: Does a hunting occur?
YES: Replace the ECM [Refer to Engine Control Module (ECM) and Powertrain Control Module (PCM)]. Then go to Step 4.
NO: It can be assumed that this malfunction is intermittent.
STEP 4. Retest the system
Q: Does a hunting occur?
YES: Return to Step 1.
NO: The procedure is complete.