Inspection Procedure 17

INSPECTION PROCEDURE 17: Deceleration Shock

COMMENT
- There may be a sudden change in airflow through the IAC, causing the vehicle to decelerate rapidly for an instant.

TROUBLESHOOTING HINTS (The most likely causes for this case:)
- Malfunction of the IAC system.

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: If necessary, you can disconnect the engine coolant temperature sensor connector and connect the harness side of the connector to another engine coolant temperature sensor that is at 20 degrees C (68 degrees F) or below.

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 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 14: Throttle Position Sensor.

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

Q: Is the sensor operating properly?

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

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