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
The signal for engaging and disengaging the air pump originates in the control unit and is routed via the air injection relay to the air pump.
Air injection occurs for a maximum of 60 seconds under the following conditions: coolant temperatures above 58°F (17°C) after starting, engine speeds below 2500 RPM, full load contact not engaged and lambda control operating.
Under these conditions, control unit energizes the electro-magnetic clutch of the air pump via the air injection relay. Simultaneously, the same relay energizes the switchover valve which in turn provides vacuum to the air injection shutoff valve. The air pump draws air from the air filter and delivers it to the exhaust ports in the cylinder head via the air injection shutoff valve, the check valve and the passages in the timing chain housing cover and the cylinder block.
The air injected from the air pump promotes oxidation of CO and HC in the catalyst. The heat created by the oxidation brings the catalyst to its operating condition quicker.
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
Disclosure: Verified tool recommendations may earn an affiliate commission at no cost to you.
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.