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.
Air Injection System: Operation
When exhaust system pressure is less than atmospheric pressure, reed valve is opened to incoming air. When exhaust pressure exceeds atmospheric pressure, reed valve is closed to incoming air. This valve also acts as a check valve.
On GLC (Federal) and 626 models, air is drawn into exhaust system downstream of the front catalytic converter. The air control valve(s) governs the injection of additional air upstream of the converter to help reduce emissions.
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
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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.
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