Hi,
the o2 sensor does not work well with my bike, when the bike is idling the sensor gives me a value of approximately 0.8V, from 2000 rpm up the o2 sensor is at 0v. I bought other o2 sensor from a junkyard but gives me the same problem. the measurement is precise (with oscilloscope)

but the sensor error appears in the instrument cluster? even if I go around with the sensor error does not come out

You will not always see an error code 24 with some O2 sensor faults as they will still generate a voltage within spec (upper and lower range), they just might be lazy, or biased towards the rich end (0.9V) or lean end (0.1V). The important thing the ECU reads is the average of the constant oscillation between high and low. You will often get an 'average' even if it's not the right one, or in the right place to give the correct fuelling.

What are you oscilloscope waveforms like? Can you post them as an image or video?

What makes you think that the O2 sensor is faulty? What symptoms are you noticing when riding/running the bike?

It's not impossible to get a low of 0.0V at the bottom of the amplitude in lean running, but it shouldn't drop much below 0.1V normally. In fact until the engine is warm, or rather the sensor is hot at around 300C, it will generate zero volts. If the heater element goes down in the sensor it will also struggle to give the right readings for the same reason.

If you have tried two sensors and they give the same results it could be the wiring loom or connector causing an open circuit in the heater circuit or a high resistance in the signal circuit which will cause lower/leaner readings than expected. Check continuity and resistance of the these circuits and the connector's condition.

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thanks for the reply, I made a video to show you the problem https://youtu.be/bPeOj573uk8

When you filmed this was the engine at full operating temperature? The ECU/fuelling will be in open loop until the coolant is at least 60C.

The readings should be a wave form something like this (averaging out around the 0.45V mark) in closed loop at idle, but only if the O2 sensor is hot enough:



If the trace is flat, that shows that there are no fuelling adjustments taking place or being made by the ECU as a result of sensor input. When the engine is started from cold it will be flat, but should flip high/low voltage 3-4 times a second at idle once warm.

Obviously if you open the throttle it will also switch to open loop and the ECU will ignore the O2 sensor.

As I said before, if both sensors you have tried do the same, then could be a wiring issue somewhere, or the heater element isn't working. Try connecting up to the two heater element wires. You should see a 0-5V square wave if the circuit is working correctly.

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I use a new oscilloscope for the test, and a new o2 sensor form ebay ( https://www.ebay.it/itm/361467036850) at idle i have the wawe form like your image, the voltage change from 0.1 to 0.75 3 times a second.
But if i try turn a little knob holding the throttle steady the trace became flat and at 0v.

Sorry I do not understand which "little knob" you are referring to?

Also, when you say "hold the throttle steady", at what rpm is this?

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