Forum Replies Created
-
Replies
-
In the sins of youth, I had a winter/daily driver and a muscle car. Although fun as hell to drive, I shouldn’t have owned that type of car at the 19-22 age range. The car got squirrely on wet pavement, the insurance, registration, parts and upgrade costs added up quickly, and it attacted a lot of negative attention – from police, crimminals, people at stoplights. For me, the dream of owning that car was better than reality.
I made the compromise to a nice, reliable daily driver. It’s not perfect, but it has a few luxuries, good fuel efficiency, and is paid off.
There seems to be a wide spectrum for POS. For me, a POS car is not reliable and is knocking on death’s door – e.g. the [stock] radio is the best thing in the car, mostly made of rust and the carpet is separating your feet from the road, houses small animals, etc.
In the sins of youth, I had a winter/daily driver and a muscle car. Although fun as hell to drive, I shouldn’t have owned that type of car at the 19-22 age range. The car got squirrely on wet pavement, the insurance, registration, parts and upgrade costs added up quickly, and it attacted a lot of negative attention – from police, crimminals, people at stoplights. For me, the dream of owning that car was better than reality.
I made the compromise to a nice, reliable daily driver. It’s not perfect, but it has a few luxuries, good fuel efficiency, and is paid off.
There seems to be a wide spectrum for POS. For me, a POS car is not reliable and is knocking on death’s door – e.g. the [stock] radio is the best thing in the car, mostly made of rust and the carpet is separating your feet from the road, houses small animals, etc.
In high school, the closest thing I had to shop was an art class focussed on stained glass – it was a small, Catholic college-prep school. I learned a lot of the material on my own, and those skills are invaluable in my field (science aka lab rat). It’s surprising and sad that many schools (where I live) have removed shop classes from their ciricula. Automotive maintenance is an open-ended problem and the abstract problem solving skills are learned in a concrete manner – all of the components can be seen, touched, tested, and even dropped on your foot.
You alluded to an issue that I call “black box mentality” where you have part with inputs and outputs, and what happens inside the box is a mystery. Although one does not need to know every detail of how one specific part works, a basic understanding helps one understand how all of the parts work together in the whole system and how to approach the problem when something is wrong.
Good luck. Being nervous is a good thing. It means that you care.
In high school, the closest thing I had to shop was an art class focussed on stained glass – it was a small, Catholic college-prep school. I learned a lot of the material on my own, and those skills are invaluable in my field (science aka lab rat). It’s surprising and sad that many schools (where I live) have removed shop classes from their ciricula. Automotive maintenance is an open-ended problem and the abstract problem solving skills are learned in a concrete manner – all of the components can be seen, touched, tested, and even dropped on your foot.
You alluded to an issue that I call “black box mentality” where you have part with inputs and outputs, and what happens inside the box is a mystery. Although one does not need to know every detail of how one specific part works, a basic understanding helps one understand how all of the parts work together in the whole system and how to approach the problem when something is wrong.
Good luck. Being nervous is a good thing. It means that you care.
An ECU is a microcontroller – a minicomputer with inputs from sensors and outputs to relays, actuators, etc. The micrcontroller has firmware, or software permanently stored on the device, which runs over-and-over in a loop that controls various engine parameters. The firmware can be updated, and this is often referred to as “reflashing the PROM”. I had a mid-80’s Buick that had this style of ECU, but it also had a lot of “analog” vacuum lines for controlling the engine.
There is another style of controller known as a PID. I don’t have much experience with these. From what I understand, it’s a set of analog circuits that provides feedback for control, like the emissions system. Basically, the PID balances output signal to an everchanging input signal in order to stabilize the system within predetermined limits. PIDs are commonplace in automated systems, so it wouldn’t surprise me if there is one or more PIDs under the hood.
An ECU is a microcontroller – a minicomputer with inputs from sensors and outputs to relays, actuators, etc. The micrcontroller has firmware, or software permanently stored on the device, which runs over-and-over in a loop that controls various engine parameters. The firmware can be updated, and this is often referred to as “reflashing the PROM”. I had a mid-80’s Buick that had this style of ECU, but it also had a lot of “analog” vacuum lines for controlling the engine.
There is another style of controller known as a PID. I don’t have much experience with these. From what I understand, it’s a set of analog circuits that provides feedback for control, like the emissions system. Basically, the PID balances output signal to an everchanging input signal in order to stabilize the system within predetermined limits. PIDs are commonplace in automated systems, so it wouldn’t surprise me if there is one or more PIDs under the hood.
[quote=”sjrobinson” post=75854]Ok I see. So does the ECU have a way to convert the signals to digital and would that really be of benefit?
And what makes the o2 signals respond quicker than others?[/quote]
Most, if not all, modern day computers, microcontrollers, electronic control systems are completely digital. Analog computers, like the Enigma encryption machine and the device that cracked it, are long gone. All of the inputs on the controller are digital or contain an analog-to-digital converter (ADC) that measures the voltage and converts it to a binary representation of zeroes and ones. The program running on the controller may convert the binary number to decimal number, like an oxygen concentration or voltage signal, and subsequently the program uses that value to perform some action.
I just thought of two “artifacts” that may appear as spiking to you. First, the ODBII scanner might autoscale the graph, so a small change in the signal look large and the noise will appear more dramatic. Also, if the O2 sensor signal varyies between two adjacent ADC steps, the digitized signal will have a step-response over time on the graph.
An O2 sensor’s response time is probably limited by diffusion of gas over the active area of the sensor. With hot flowing exhaust, diffusion is very rapid. I’m guessing it’s not the response time of both sensors that appear to be slow. The time it takes for a portion of exhaust gas to pass between the 2 sensors by way of the catalytic converter probably should not exceed a couple of seconds. It’s possible that there is some lag between the ODBII scanner and the ECU.
[quote=”sjrobinson” post=75854]Ok I see. So does the ECU have a way to convert the signals to digital and would that really be of benefit?
And what makes the o2 signals respond quicker than others?[/quote]
Most, if not all, modern day computers, microcontrollers, electronic control systems are completely digital. Analog computers, like the Enigma encryption machine and the device that cracked it, are long gone. All of the inputs on the controller are digital or contain an analog-to-digital converter (ADC) that measures the voltage and converts it to a binary representation of zeroes and ones. The program running on the controller may convert the binary number to decimal number, like an oxygen concentration or voltage signal, and subsequently the program uses that value to perform some action.
I just thought of two “artifacts” that may appear as spiking to you. First, the ODBII scanner might autoscale the graph, so a small change in the signal look large and the noise will appear more dramatic. Also, if the O2 sensor signal varyies between two adjacent ADC steps, the digitized signal will have a step-response over time on the graph.
An O2 sensor’s response time is probably limited by diffusion of gas over the active area of the sensor. With hot flowing exhaust, diffusion is very rapid. I’m guessing it’s not the response time of both sensors that appear to be slow. The time it takes for a portion of exhaust gas to pass between the 2 sensors by way of the catalytic converter probably should not exceed a couple of seconds. It’s possible that there is some lag between the ODBII scanner and the ECU.
Are ground loops a concern here – where a different amounts of current flow through the 2 paths, which create a potential difference between the 2 ground points? In modern cars, there is a lot of circuitry and sensors that might use the ground to provide a reference voltage. A ground loop might also create some feedback in the audio system as well.
If the car originally came with cables connected to the chassis and engine, there was probably a good reason for the 2 cables, such as the engine was somewhat isolated from the chassis or did not provide sufficient current flow, etc.
I’m curious to the answer myself.
Are ground loops a concern here – where a different amounts of current flow through the 2 paths, which create a potential difference between the 2 ground points? In modern cars, there is a lot of circuitry and sensors that might use the ground to provide a reference voltage. A ground loop might also create some feedback in the audio system as well.
If the car originally came with cables connected to the chassis and engine, there was probably a good reason for the 2 cables, such as the engine was somewhat isolated from the chassis or did not provide sufficient current flow, etc.
I’m curious to the answer myself.
Most ODB code readers, like the loaner units available at auto parts stores, have an erase function.
In the past, you could disconnect the negative battery terminal for several minutes to reset the system. I don’t know if this method still works. Just make sure you have the radio unlock code first.
Most ODB code readers, like the loaner units available at auto parts stores, have an erase function.
In the past, you could disconnect the negative battery terminal for several minutes to reset the system. I don’t know if this method still works. Just make sure you have the radio unlock code first.
Thanks for bringing that up
Any O2 that you have to wire in manually (universal style) I wont touch here in the shop, they cause far more problems than they solve. The butt connectors are prone to corrode (especially rear O2s as the wring is often under the car) and will actually make a sensor lazy or out of range and sometimes wont set a code.
From what I read, there was a very specific procedure for splicing the connector, but I don’t understand the reasoning behind it. Also, many vendors won’t allow you to return a sensor that has been taken out of the box. So, spending more upfront may save you both money and frustration in the long run.
Just for clarification, I did not mean that the part has to be purchased from the dealership. I meant to buy an aftermarket sensor that is labelled “OEM style” or “direct replacement”.
Thanks for bringing that up
Any O2 that you have to wire in manually (universal style) I wont touch here in the shop, they cause far more problems than they solve. The butt connectors are prone to corrode (especially rear O2s as the wring is often under the car) and will actually make a sensor lazy or out of range and sometimes wont set a code.
From what I read, there was a very specific procedure for splicing the connector, but I don’t understand the reasoning behind it. Also, many vendors won’t allow you to return a sensor that has been taken out of the box. So, spending more upfront may save you both money and frustration in the long run.
Just for clarification, I did not mean that the part has to be purchased from the dealership. I meant to buy an aftermarket sensor that is labelled “OEM style” or “direct replacement”.
I recently diagnosed and replaced a bad AFR sensor on my car. Like the other posters alluded to, an outlier reading can generate an error code or you may also have a pending code in memory. Clear the codes and see if they reappear.
Also, many ODBII code readers give a generic description with an error code and Honda will have a more specific description, which was more helpful in my case. The Helms manual for my car (TSX) states that a P0141 is a malfunction with the heater circuit in the secondary heated O2 sensor – I don’t know if this applies to your car or not however.
If the above is true, then Eric’s video shows you how to diagnose a faulty heater circuit with a multimeter. The black leads go to the heating element while the blue and white wires go to the O2 sensor. Measure the resistance between the black leads. If the heating element is good, the resistance should be on the order of tens of Ohms. A bad heating element will have a resistance 100 kOhms or higher because no current can flow through the heater, and a code is generated because the emission system is not operating at some prescribed level.
Finally, if the O2 sensor requires replacement, try to use a direct replacment. From what I’ve read for my car, Hondas can have issues with universal sensors, especially the ULEV models. You might want to consider the Denso or NGK part (whomever made the OEM part for your car).