Inspection Procedure 9

INSPECTION PROCEDURE 9: 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 IAC system.
- Malfunction of the throttle body.

DIAGNOSIS

Required Special Tools:
- MB991958: Scan Tool (M.U.T.-III Sub Assembly)
- MB991824: V.C.I.
- MB991827: USB Cable
- MB991911: Main Harness B

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 DTC set?

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

NO: Go to Step 2.

STEP 2. Check the idle air control (IAC) motor operation sound.




1. Check that the engine coolant temperature is 20 degrees C (68 degrees F) or below.

NOTE: Disconnecting the engine coolant temperature sensor connector and connecting the harness side of the connector to another engine coolant temperature sensor that is at 20 degrees C (68 degrees F) or below is also acceptable.

2. Check the operation sound of the IAC motor can be heard after the ignition is switched to the "ON" position (but without starting the engine).
- An operation sound should be heard.

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

Q: Did you hear the operation sound?

YES: Go to Step 3.

NO: Refer to, DTC P0506 - Idle Control System RPM Lower Than Expected P0506, DTC P0507 - Idle Control System RPM Higher Than Expected P0507.

STEP 3. Using scan tool MB991958, check data list.

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 the following items in the data list. Refer to, Data List Reference Table. Data List Reference Table & Normal Scan Data Values
a. Item 21: Engine Coolant Temperature Sensor.
b. Item 28: A/C Switch.

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

Q: Are they operating properly?

YES: Go to Step 4.

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

STEP 4. Adjust the basic idle speed.

Refer to On-vehicle Service - Basic Idle Speed Adjustment for the adjustment procedure.

Standard value: 850 ± 50 r/min

Q: Is the Idle speed normal?

YES: Refer to Throttle Body On-vehicle Service - Clean the throttle valve area.

NO: The check is completed.