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Wiring Fundamentals: Oxygen Sensors

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Oxygen Sensors

02.24

00:00 - Oxygen sensors fall into one of two categories, either narrow band, or wideband.
00:05 Most commonly in the automotive performance world, you will be dealing with wideband oxygen sensors, as they give us an accurate reading as to the real air to fuel ratio that the vehicle is running.
00:14 Whereas a narrowband sensor can only tell us if the engine is rich or lean, but not by how much.
00:20 Wideband oxygen sensors require specialised electronics to interpret their output signal.
00:25 Your ECU may have these electronics built into it, in which case you'll find dedicated pins that the sensor needs to be wired to described in your ECU's documentation.
00:34 If your ECU does not have the necessary electronics to interpret the signals from a wideband oxygen sensor, you can use an external wideband controller.
00:43 This device converts the output signal of the wideband sensor into a voltage signal you can then wire to any of the analog voltage inputs on your ECU.
00:51 Wideband oxygen sensors only operate once they are above a minimum temperature.
00:55 To achieve this temperature quickly after a vehicle is started, they contain a heater element.
01:00 Correct wiring of this heater element is critical to the sensor's operation, and we will cover it in the actuators section of the course.
01:06 Particularly important in the case of external wideband controllers, is the issue of ground offsets we discussed in the analog voltage sensor section of the course.
01:14 The majority of wideband controllers on the market generate their analog voltage output signal referenced to their power ground.
01:21 When the ECU reads this analog voltage signal it references it to its internal sensor ground level.
01:27 As the power ground and sensor ground levels can be offset from one another, the voltage the ECU reads can be different from what the wideband controller is actually generating.
01:36 This causes an error to be seen in the air to fuel ratio within the ECU.
01:41 Because the range of air to fuel ratios we typically use when tuning an engine is quite a narrow section of the sensor's full resolution, a small error in this voltage level can result in a large error in the air to fuel ratio that we see.
01:54 For this reason, many wideband controllers have moved to determining the air to fuel ratio internally and then sending this value out to the ECU via a CAN bus network connection.
02:04 This direct data transmission eliminates the problem of ground offsets and has the added benefit of allowing the wideband controller to send diagnostic data on the current state of the oxygen sensor.
02:14 Allowing a failure to be diagnosed more easily.