O2 sensor resistor
Elder User
Joined: Jul 2004
Posts: 620
Likes: 1
From: Toronto, ON
Ok, definately learned something new
I had no idea the O2 sensor is actually a generator! It takes the gasses and converts it to electricity. The power sent to the o2 sensor is only used to heat up the sensor so it can operate properly.
I had originally thought that a constant supply of power was sent to the o2 sensor, and through some sort of electro-chemical process, the a varied amount of this power was sent back to the PCM.
I had no idea the O2 sensor is actually a generator! It takes the gasses and converts it to electricity. The power sent to the o2 sensor is only used to heat up the sensor so it can operate properly.I had originally thought that a constant supply of power was sent to the o2 sensor, and through some sort of electro-chemical process, the a varied amount of this power was sent back to the PCM.
Postmaster
Joined: Jan 2003
Posts: 4,417
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From: Durham, NC
Originally Posted by Silver Streak
I'm not going to nit pick with you. The computer only know if it's rich or lean, not how much. That's a digital answer, not analog.
this, is the signal pulse width going to the injectors, it's a gradual "sweep" in pulse width, not a "step" in pulse width (in closed loop) again, analog control. Have you ever scoped the injector pulse?
Postmaster
Joined: May 2002
Posts: 3,241
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From: Broken Arrow, OK
The injector pulse width and the O2 signal are two different things. I've scoped more things than I can remember. All I am saying is that the computer interprets the O2 sensor input digitally; it's either rich or lean. It adjusts the pulse width accordingly.
The injector pulse itself really has nothing to do with this. It is based on the current required to accelerate the pintle and the current required to maintain an open condition for the current of the pulse.
The injector pulse itself really has nothing to do with this. It is based on the current required to accelerate the pintle and the current required to maintain an open condition for the current of the pulse.
Postmaster
Joined: Jan 2003
Posts: 4,417
Likes: 3
From: Durham, NC
Originally Posted by Silver Streak
The injector pulse width and the O2 signal are two different things. I've scoped more things than I can remember. All I am saying is that the computer interprets the O2 sensor input digitally; it's either rich or lean. It adjusts the pulse width accordingly.
The injector pulse itself really has nothing to do with this. It is based on the current required to accelerate the pintle and the current required to maintain an open condition for the current of the pulse.
The injector pulse itself really has nothing to do with this. It is based on the current required to accelerate the pintle and the current required to maintain an open condition for the current of the pulse.
Postmaster
Joined: May 2002
Posts: 3,241
Likes: 3
From: Broken Arrow, OK
I can't believe I've fallen into the trap of doing actual research and reaching back in time to things learned long ago.
Click here and here to see what Toyota has to say about it. Either above of below .45 with no further recognition sounds pretty digital to me. Those both look like the same document, but word things differently.
Since you are so well versed in using a scope I'm sure you are well aware that a true square wave (aka digital dignal) can't be created because it is impossible to instantaneously generate a voltage. There must always be a transition to and from the limit of the signal. These transitions are the curves you see in the graph. It is true that the O2 sensor can give a reading between 0 and 1. It has to in order to function. You can't go from 0 to 1 without passing through all points in between. The O2 sensor shows voltages between the two limits when it doesn't have time to completely generate its full voltage or completely dissipate its existing voltage before swinging the other way. For example: If it is sitting at 1 volt and the mixture suddenly goes lean it begins to transition to 0 volts. If the mixture goes rich before it gets to 0 volts it must read something in between.
From Honda:
Closed Loop
In closed loop operation the ECU uses one or more oxygen sensors as a feedback loop in order to adjust the fuel mixture. This gives the name ‘closed loop’ from the closed feedback loop. The ECU won’t run in a closed feedback loop all the time, so ‘open loop’ is used to describe the operation of the ECU when the mixture is not being adjusted in this way (usually when the engine is cold or when running under high load).
In closed loop operation the ECU uses the oxygen sensor to tell if the fuel mixture is rich or lean. However, due to the characteristics of the oxygen sensor it can’t tell exactly how rich or lean, it only knows that the mixture is richer or leaner than optimum. The ECU will enrich the mixture if the oxygen sensor shows that the mixture is lean, and lean the mixture if it looks rich. The result of this is that the mixture will swing back and forward around the stoichiometric point.
Closed Loop
In closed loop operation the ECU uses one or more oxygen sensors as a feedback loop in order to adjust the fuel mixture. This gives the name ‘closed loop’ from the closed feedback loop. The ECU won’t run in a closed feedback loop all the time, so ‘open loop’ is used to describe the operation of the ECU when the mixture is not being adjusted in this way (usually when the engine is cold or when running under high load).
In closed loop operation the ECU uses the oxygen sensor to tell if the fuel mixture is rich or lean. However, due to the characteristics of the oxygen sensor it can’t tell exactly how rich or lean, it only knows that the mixture is richer or leaner than optimum. The ECU will enrich the mixture if the oxygen sensor shows that the mixture is lean, and lean the mixture if it looks rich. The result of this is that the mixture will swing back and forward around the stoichiometric point.
Since you are so well versed in using a scope I'm sure you are well aware that a true square wave (aka digital dignal) can't be created because it is impossible to instantaneously generate a voltage. There must always be a transition to and from the limit of the signal. These transitions are the curves you see in the graph. It is true that the O2 sensor can give a reading between 0 and 1. It has to in order to function. You can't go from 0 to 1 without passing through all points in between. The O2 sensor shows voltages between the two limits when it doesn't have time to completely generate its full voltage or completely dissipate its existing voltage before swinging the other way. For example: If it is sitting at 1 volt and the mixture suddenly goes lean it begins to transition to 0 volts. If the mixture goes rich before it gets to 0 volts it must read something in between.
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Postmaster
Joined: Jan 2003
Posts: 4,417
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From: Durham, NC
Originally Posted by Silver Streak
I can't believe I've fallen into the trap of doing actual research and reaching back in time to things learned long ago.
Click here and here to see what Toyota has to say about it. Either above of below .45 with no further recognition sounds pretty digital to me. Those both look like the same document, but word things differently.
Since you are so well versed in using a scope I'm sure you are well aware that a true square wave (aka digital dignal) can't be created because it is impossible to instantaneously generate a voltage. There must always be a transition to and from the limit of the signal. These transitions are the curves you see in the graph. It is true that the O2 sensor can give a reading between 0 and 1. It has to in order to function. You can't go from 0 to 1 without passing through all points in between. The O2 sensor shows voltages between the two limits when it doesn't have time to completely generate its full voltage or completely dissipate its existing voltage before swinging the other way. For example: If it is sitting at 1 volt and the mixture suddenly goes lean it begins to transition to 0 volts. If the mixture goes rich before it gets to 0 volts it must read something in between.
Click here and here to see what Toyota has to say about it. Either above of below .45 with no further recognition sounds pretty digital to me. Those both look like the same document, but word things differently.
Since you are so well versed in using a scope I'm sure you are well aware that a true square wave (aka digital dignal) can't be created because it is impossible to instantaneously generate a voltage. There must always be a transition to and from the limit of the signal. These transitions are the curves you see in the graph. It is true that the O2 sensor can give a reading between 0 and 1. It has to in order to function. You can't go from 0 to 1 without passing through all points in between. The O2 sensor shows voltages between the two limits when it doesn't have time to completely generate its full voltage or completely dissipate its existing voltage before swinging the other way. For example: If it is sitting at 1 volt and the mixture suddenly goes lean it begins to transition to 0 volts. If the mixture goes rich before it gets to 0 volts it must read something in between.
used a SEM to acquire waveforms on internal nets an a chip, using a secondary electron emissions technique, without mechanically touching the net!!
Notice the "running too lean", and "running too rich" waveforms, and how there is an offset below, and above .45V. What you are seeing are analog
signals, NOT DIGITAL. If the PCM processed the NORMAL, TOO RICH, and TOO LEAN, waveforms as digital, it would not be able to distinguish between them. Therefore, O2 signals are processed as analog signals. Did you understand what an A to D was in my previous post????
Last edited by Bob Ayers; Dec 23, 2005 at 03:21 PM.
Postmaster
Joined: May 2002
Posts: 3,241
Likes: 3
From: Broken Arrow, OK
I thought you were done? Yes, I know what an A to D is. Do you comprehend what was published by both Honda and Toyota in the above post? Do you understand the difference between a narrow band O2 sensor that is used in production vehicles and a wide band O2 sensor that is more than likely piggy backed on your precious Haltech? A narrow band can't tell the difference between 14:1 and 10:1, it just knows that it's richer than stoich than stoich. The same applies to ratios that are lean of stoich. The wide band can tell you anything from about 9 or 10:1 to straight air.
Produce a published document from a reputable source and I might start to believe you have a clue!
Produce a published document from a reputable source and I might start to believe you have a clue!
Posting Guru
Joined: Sep 2004
Posts: 1,556
Likes: 5
This is an interesting topic as I have no idea.
My first search resulted in this:
Analog-to-digital converters - These devices read the outputs of some of the sensors in the car, such as the oxygen sensor. The output of an oxygen sensor is an analog voltage, usually between 0 and 1.1 volts (V). The processor only understands digital numbers, so the analog-to-digital converter changes this voltage into a 10-bit digital number.
Thats if anyone believes howstuffworks.com...haha
http://computer.howstuffworks.com/car-computer2.htm
Seems the other results I read back that up...so maybe your both right...
A. The O2 sensor puts off an analog signal but
B. This signal is converted to digital so the ecu can understand it.
Maybe?
What I gather form this conversation and put into my layman terms, the debate is whether modifying the signal to the ecu, from the O2 would help performance. From all links read thus far, the toyota ones included, be it digital or analog, all the comptuer understands with a narrowband is: rich, ideal, lean. All this is determined by 14.25volt, if you trick the O2 to read less, the ecu will constantly try and lean the mixture, if you trick it to read more, it will wanna try and richen the mixture...so no benefit.
My first search resulted in this:
Analog-to-digital converters - These devices read the outputs of some of the sensors in the car, such as the oxygen sensor. The output of an oxygen sensor is an analog voltage, usually between 0 and 1.1 volts (V). The processor only understands digital numbers, so the analog-to-digital converter changes this voltage into a 10-bit digital number.
Thats if anyone believes howstuffworks.com...haha
http://computer.howstuffworks.com/car-computer2.htm
Seems the other results I read back that up...so maybe your both right...
A. The O2 sensor puts off an analog signal but
B. This signal is converted to digital so the ecu can understand it.
Maybe?
What I gather form this conversation and put into my layman terms, the debate is whether modifying the signal to the ecu, from the O2 would help performance. From all links read thus far, the toyota ones included, be it digital or analog, all the comptuer understands with a narrowband is: rich, ideal, lean. All this is determined by 14.25volt, if you trick the O2 to read less, the ecu will constantly try and lean the mixture, if you trick it to read more, it will wanna try and richen the mixture...so no benefit.
Last edited by Motorhead351; Dec 27, 2005 at 09:37 AM.
Posting Guru
Joined: Sep 2004
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Well, just to get a better understanding of this conversation, I consulted someone thats devoted alot of time to automotive ecu's, not taking anything away from anyone that has posted already.
I asked, does a narrow band O2 put off an analog or digital signal?
Answer:
The narrow band sensor signal is essentially on/off, which is what digital signals are.
However, when looked at closely, there is some slope at the switching point so the transition is not 100% either on or off, so that more like an anolog signal. And there's certainly no logic device in the sensor, it's all chemically driven.
So it's really one of those things where the signal doesn't fit the definitions paticualarly well, and you can consider it to be either, depending on how closely you are looking, and how you define "digital" and "analog".
So as I gathered earlier, seems your both right...
I asked, does a narrow band O2 put off an analog or digital signal?
Answer:
The narrow band sensor signal is essentially on/off, which is what digital signals are.
However, when looked at closely, there is some slope at the switching point so the transition is not 100% either on or off, so that more like an anolog signal. And there's certainly no logic device in the sensor, it's all chemically driven.
So it's really one of those things where the signal doesn't fit the definitions paticualarly well, and you can consider it to be either, depending on how closely you are looking, and how you define "digital" and "analog".
So as I gathered earlier, seems your both right...
Lead Driver
Joined: Nov 2002
Posts: 9,557
Likes: 44
From: Concord, NC
So what happens at Stoich. ratio? That's .5V, right? The narrow band is exactly that, a narrow window in which it senses. It can accurately measure small variances from stoich, but like you guys are saying, once it is out of the narrow band, it's rich or lean, giving no exact measure. The A/F ratio is always bouncing lean/rich in EFI vehicles in order to enhance catalyst efficiency. Those toyota references are so dumbed down, I wouldn't hold them for much technical merit. During light cruise, fuel is trimmed lean and EGR is activated. How does the computer know how lean is safe if it only knows lean and rich? If it is purely analog on/off signal, why is the sensor deemed bad (and computer/driveability affected) when there are shifts in the voltage trace (see diagram in toyota documentation)?
For the original question, a resistor in line with the O2 sensor is going to be a stab in the dark for trying to fool the computer and most likely won't work. It would cause a CEL, but if you want the thing to run the wrong mixture, just unplug the O2 sensor completely. It'll run the fuel straight from the tables.
For the original question, a resistor in line with the O2 sensor is going to be a stab in the dark for trying to fool the computer and most likely won't work. It would cause a CEL, but if you want the thing to run the wrong mixture, just unplug the O2 sensor completely. It'll run the fuel straight from the tables.
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