Inspection Procedure 8

Inspection procedure 8: Idle speed is high (improper idle speed)

COMMENT
- In such cases as the above, the cause is probably that the intake air volume during idle is too great.

TROUBLESHOOTING HINTS (The most likely causes for this case:)
- Malfunction of the engine coolant temperature sensor signal.
- Malfunction of the accelerator pedal position sensor(main) signal.
- Malfunction of the accelerator pedal position sensor(sub) signal.
- Malfunction of the A/C switch signal.
- Malfunction of the power steering pressure switch signal.
- Malfunction of the evaporative emission control system.
- Malfunction of the ECM.

DIAGNOSIS

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

STEP 1. Using scan tool MB991958, read the diagnostic trouble code (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.
2. Turn the ignition switch to the "ON" position.
3. Read the DTC.
4. Turn the ignition switch to the "LOCK" (OFF) position.

Q: Is any DTC set?

YES : Refer to Diagnostic Trouble Code Chart. Diagnostic Trouble Code Descriptions

NO : Go to Step 2.

STEP 2. Using scan tool MB991958, check data list.

1. Turn the ignition switch to the "ON" position.
2. Check the following item in the data list. Refer to Data List Reference Table. Datal List Reference Table
a. Item 6: Engine Coolant Temperature Sensor.
b. Item 11: Accelerator pedal position sensor (main)
c. Item 12: Accelerator pedal position sensor (sub)
d. Item 76: A/C switch
e. Item 83: Power steering pressure switch

3. Turn the ignition switch to the "LOCK" (OFF) position.

Q: Is the sensor operating properly?

YES : Refer to Emission Control System - Evaporative Emission Control System - Evaporative Emission Purge Solenoid Check. Evaporative Emission Purge Solenoid Check

NO : Repair or replace it. Then confirm that the malfunction symptom is eliminated.