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.
Open Loop Mode
During start-up and acceleration, the EFC controller disregards any oxygen sensor signals. This results in temporarily richer mixtures for better performance. During warm-up, the air injection system supplies air to the exhaust manifold (ahead of both converters). This additional air allows complete oxidation of HC and CO in the main converter during this rich mixture period (NOx is not a factor since low temperatures do not create this emission). This "burning" helps quickly raise exhaust system temperatures, allowing the oxygen sensor and 3-way catalyst to warm-up faster.
At normal operating temperatures, the air switching valve in the air injection system directs additional air from the exhaust ports to the exhaust pipe, just ahead of the oxidation catalyst. The Closed Loop Mode comes into operation.
Use the Manual With the Right Hardware
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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.