Test Description

The numbers below refer to the step numbers in the diagnostic procedure.

1. 1  - The Diagnostic System Check-Engine Controls prompts the technician to complete some basic checks and store the Freeze Frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.
2. 4  - This step tests whether the PCM can operate the IAC valve with the scan tool. The IAC valve can be commanded to increase and/or decrease engine speed by using the scan tool RPM Control function. The RPM Control function of the scan tool is disabled when any DTCs are set, and when the engine is less than the normal operating temperature of 80°C (176°F).
3. 5  - This step checks the operation of the electrical load idle-up circuits. If there is no increase in the IAC Duty Cycle percentage when the accessory is turned on, the idle-up circuit may be inoperative or always on.
4. 6  - This step checks the operation of the A/C idle-up circuits. If there is no increase in the IAC Duty Cycle percentage when the A/C compressor is engaged, the idle-up circuit may be inoperative or always ON.
5. 10  - This step checks the electrical circuits between the IAC valve and the PCM.
6. 11  - This step determines whether the PCM is attempting to control the IAC valve. Each IAC coil control circuit should indicate a high voltage of 12 volts or more, and then a low voltage of 0.0-1.0 volts as the PCM commands changes in the engine speed. Remember to clear any DTCs and run the engine until the engine reaches a normal operating temperature before attempting RPM Control with the scan tool.