With Scan Tool

Diagnostic Chart:

DESCRIPTION
The Powertrain Control Module (PCM) controls the engine idle speed through the Idle Air Control (IAC) valve. The IAC valve opens and closes the idle air passage in the throttle body according to signals from the PCM. The PCM determines the correct engine idle speed by using information from various sensors and from various switches. The PCM increases AC duty when engine speed drops below a specified value. The PCM maintains a smooth idle and a stable idle by monitoring certain engine components in order to respond to changes in engine load. The engine idle speed is a factory set calibration and is not adjustable.

DIAGNOSTIC AIDS
DO NOT attempt to adjust the IAC valve or the throttle-valve opening. The engine IAC valve and the idle speed are not adjustable. Operate the IAC valve with the scan tool by selecting the appropriate Output Control feature. Command the IAC valve to increase and to decrease the engine idle speed. Diagnose the faulty component, and replace the faulty component, or locate and repair the cause of the idle concern. Check for any of the following conditions if the IAC valve fails to control the engine speed when commanded by the scan tool:
^ Vacuum leaks
^ Blockage of the idle air passage
^ Incorrect PCV system operation
^ Excessive accessory engine loads
^ A faulty IAC valve
^ Faulty electrical connections in the IAC valve electrical circuit

If the engine idle speed is a concern when the air conditioning or the windshield defroster are running, check the A/C idle-up signal. Refer to A/C Idle Circuit Diagnosis. Component Tests and General Diagnostics

If the engine idle speed is a concern when the headlights, the blower motor, or the rear defogger are on, check the electrical load idle-up signal. Refer to Electrical Load Idle-Up Signal Diagnosis. Component Tests and General Diagnostics

TEST DESCRIPTION
The numbers below refer to the step numbers in the diagnostic table.
1. The Powertrain OBD system check prompts the technician to complete some basic checks, and to store the applicable Freeze Frame data on the scan tool. This creates an electronic copy of the data that was taken when the fault occurred. The scan tool stores the information for later reference.
2. This step checks the engine idle speed with the engine at normal operating temperatures and without a load. DO NOT attempt to adjust the IAC valve or the throttle valve opening. The engine IAC valve and the idle speed are not adjustable. Locate the faulty component, and replace the faulty component, or repair the cause of the idle concern.
3. This step checks that the opening in the idle air passage of the IAC valve is within the expected percentage. A DTC P0505 may set if this parameter stays outside the specified value.
4. This step checks for vacuum leaks or for faulty connections in the fuel injection and in the EVAP control systems.
5 This step checks the accelerator control cable for a binding or for a condition that is adjusted incorrectly.