Variable Induction System: Testing and Inspection

Chart C-2D:

IAC Circuit:

CIRCUIT DESCRIPTION:

The secondary air control system is used to control air to the secondary intake valves within engine speed is above about 5000 rpm. Using this system allows for reduced intake air at idle to improve idle quality and then opens at higher rpm to improve engine performance and increase horse power. This system consists of the secondary port intake valves mounted in the lower intake manifold and a vacuum operated diaphragm which moves the secondary valve linkage. The vacuum to the diaphragm is turned "ON" or "OFF" by a vacuum switching solenoid which is electrically operated by the Electronic Control Module (ECM).

TEST DESCRIPTION: The numbers below refer to circled numbers on the diagnostic chart.

1. Without the proper vacuum being available at the solenoid the system will not function properly.

2. When the ignition is "ON" and the engine not running the solenoid should not be energized. Since the solenoid is normally closed the vacuum should not be able to pass to the actuator.

3. With the diagnostic terminal grounded the ECM should ground WHT/BLU which should energize the solenoid and allow vacuum to pass to the actuator.

4. This step checks the ability of the vacuum actuator to be able to move the secondary intake valve linkage.

5. This step as well as the following steps checks for circuit continuity.