Internally, wideband O2 sensors and A/F sensors appear to be similar to conventional zirconia planar oxygen sensors. On some of the early Toyota OBD II applications, the PCM converts the A/F sensor voltage to look like that of an ordinary oxygen sensor (this was done to comply with the display requirements of early OBD II regulations). The sensor's output signal is then processed by the PCM, and can be read on a scan tool as the air/fuel ratio, a fuel trim value and/or a voltage value depending on the application and the display capabilities of the scan tool.įor applications that display a voltage value, anything less than the reference voltage indicate a rich air/fuel ratio while voltages above the reference voltage indicates a lean air/fuel ratio. The PCM sends a control reference voltage (typically 3.3 volts on Toyota A/F sensor applications, 2.6 volts on Bosch and GM wideband sensors) to the sensor through one pair of wires, and monitors the sensor's output current through a second set of wires. And when the air/fuel ratio becomes progressively richer, the current reverses course and flows in the negative direction. At the "stoichiometric" point when the air/fuel mixture is perfectly balanced (14.7 to 1), which is also referred to as "Lambda", the current flow from the sensor stops and there is no current flow in either direction. The current signal gradually increases in the positive direction when the air/fuel mixture becomes leaner. By comparison, a wideband O2 sensor or A/F sensor provides a gradually changing current signal that corresponds to the exact air/fuel ratio.Īnother difference is that the sensor's output voltage is converted by its internal circuitry into a variable current signal that can travel in one of two directions (positive or negative).
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This makes it better suited to today's low emission engines, and also for tuning performance engines.Īn ordinary oxygen sensor is really more of a rich/lean indicator because its output voltage jumps up to 0.8 to 0.9 volts when the air/fuel mixture is rich, and drops to 0.3 volts or less when the air/fuel mixture is lean. But unlike an ordinary oxygen sensor, the output signal from a wideband O2 sensor or A/F sensor does not change abruptly when the air/fuel mixture goes rich or lean.
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Like an ordinary oxygen sensor, it reacts to changing oxygen levels in the exhaust. Wideband Oxygen sensors (which may also be called Wide Range Air Fuel (WRAF) sensors) and Air/Fuel (A/F) Sensors, are replacing conventional oxygen sensors in many late model vehicles.Ī wideband O2 sensor or A/F sensor is essentially a smarter oxygen sensor with some additional internal circuitry that allows it to precisely determine the exact air/fuel ratio of the engine. Wideband O2 Sensors and Air/Fuel (A/F) Sensors by Larry Carley copyright 2019
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Wideband with binary editor manuals#
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