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 Fuel Ratio (A/F) Sensor 1: Description
The A/F sensor 1 is mounted on the exhaust manifold, and transmits the signal of detected oxygen concentration in the exhaust gas to ECM.
While O2 sensor changes output voltage by ON/OFF (rich/lean) mode within a narrow range of the stoichiometric ratio, the A/F sensor changes output voltage between 0 - 4 V for a wide range of air fuel ratio.
ECM judges the state of air fuel ratio with this signal, and precisely controls air fuel ratio to match the stoichiometric ratio. Also, the sensor is equipped with heater for maintaining the activated state.
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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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