Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Auxiliary Intake Air Control System
The auxiliary intake air control solenoid is operated by the Powertrain Control Module (PCM). The PCM supplies a ground path to the solenoid control circuit using an internal solid state device called a driver. The auxiliary intake air control system supplies additional air to the engine during hard acceleration and when operating under high engine loads. The lower air cleaner housing has two inlet air ducts. The auxiliary inlet air duct is opened or closed by a vacuum operated door. Manifold vacuum is supplied to the door motor by a vacuum solenoid. When the PCM commands the solenoid ON, voltage on the control circuit should be near zero or low. When the PCM commands the solenoid OFF, voltage on the control circuit should be near battery voltage or high. When the solenoid is energized, manifold vacuum is applied to the vacuum motor and the auxiliary inlet air duct door is closed. See Fig 1 . For diagnosis of auxiliary intake air system refer to SYSTEM & COMPONENT TESTING - 1.8L VIBE article.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.