The Air/Fuel Ratio (A/F) sensor is similar to the narrow range oxygen sensor. Though it appears similar to the oxygen sensor, it is constructed differently and has different operating characteristics.
The A/F sensor is also referred to as a wide range or wide ratio sensor because of its ability to detect air/fuel ratios over a wide range.
The advantage of using the A/F sensor is that the ECM can more accurately meter the fuel reducing emissions. To accomplish this, the A/F sensor:
• operates at approximately 650'C (1200'F), much hotter than the oxygen sensor 400'C (750'F).
• changes its current (amperage) output in relation to the amount of oxygen in the exhaust stream.
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