Nice intro / refresher! Props to your wife for asking questions! A lot of things in school didn't make sense to me (due to the language barrier in the early years of moving to Canada)... and I was always too chicken to speak up to ask for clarification (would not have been cool I thought). I'm still the quiet type... but thank goodness for the internet, youtube & all the great channels that I can refresh & learn from. Thanks Terry!
+Thomas EXOVCDS Always a pleasure Thomas and good to see your comment. And no need to be the quiet type as you're amongst friends and have a lot of knowledge to share yourself. Thanks for dropping in and sharing your thoughts!
Terry your tutorial videos are fantastic and your teaching manner is over the top. thank you for taking the time to post. Looking forward to seeing more. thanks again.
Hi Terry. I found you again after a google search, to decide whether my occasionally unreliable dashboard fuel gauge was the dash stepper motor or the sending unit inside the tank. As always, I like your clear thinking. Of course dealing with an intermittent problem can be frustrating. I will attach my scan tool, make a baseline plot plot of fuel gauge voltage reading when the gauge is working, then wait for a convenient time when it fails. Then when the dash shows a bad reading, I'll use the scan tool to decide whether the stepper motor is accurately representing the voltage coming from the sending unit. I suspect the sending unit is on its way out, but a stepper motor would be so much easier to swap out, ha ha.
Your videos are terrific. Love watching them. Best electrical videos I have come across. Maybe you can explain what a pull up resistor does inside the PCM in one of your videos.
Excellent video. My son has a 2006 Chevy Silverado with a P0449 evaporative emission vent solenoid control circuit, and a p0463 fuel level circuit sensor one high voltage. Could the p0463 fuel level circuit code be causing the P0449 evaporative emissions code?
More than likely you have two separate issues. The P0449 is telling you that you have a circuit issue with the vent solenoid. The solenoid could be open, wire broke or not likely an ECM issue. And the fuel level sending unit is a common issue on GM issues where the fuel sending unit is the most likely cause.
Nice- very good level of understanding for someone to begin their repair with. Terry I always found the words "infinite resistance" perplexing , is there any difference than as in a "open circuit" ?
very interesting video...here comes the question and let me first begin with i have purchased many voltage testers that have all rusted in my tool box cause i never learned how to use them lol..Since the ohm calculations are so precise on the level of a empty to a full tank of gas why do i get better gas mileage on the first half of the tank than the second half when the needle goes the same amount of distance on the gauge?? thanks Terry
+RICKAFIX Hey Rick and hope you're doing well. Your gas mileage should be the same throughout although the rate of decline for the needle on the gauge could vary. As one viewer pointed out, the different configurations of fuel tanks could cause this. In this video, I was thinking more of a fuel tank that was symmetrical in depth. In the second video, I'll cover the different tank configurations and how this could vary the needle which may not be linear. Take care Rick...
My car, Civic Es 8 has a problem of indicating a wrong fual level.when i stop the vehicle with some amount of fuel it indicates correctly on my instrument cluster gauge. But next day when I start the car, the fuel level seems to go down suddenly.After driving 15 to 20 mins, it goes up again like it shows before, this happened after i changed my fual pump with floatr, could you please help me on this??
OH, so on a rheostat, if I was looking at volts I might see very little change and think the component was bad, but knowing some are rheostats, I should look at the amps and see the great variation. I just learned something new. Did I get it right?
+DE Nichols Hi DE...when one speaks of a rheostat, it's more of how it's wired as I point out in the videos which is more of varying current. The potentiometer where it's name is potential, (voltage), varies voltage. With a potentiometer, the current wouldn't vary through the total resistance of the pot as its resistance is fixed even if you were to move the wiper. Yet, the voltage will vary from one of the outside legs to the wiper. When you see a pot wired with its wiper connected to one of the outside legs, like fuel sending units, folks in the industry will say that its a rheostat which would vary the current, but at the same time it will vary the voltage too because the total resistance of the rheostat will change because the wiper is part of the function now. Even still, the computer is still looking at a voltage change. You could see the variation in current, but it would be an extra step to wire an ammeter in series with it. I would just measure the voltage across the sending unit as I show which is faster. Thanks for leaving a comment DE!!!
+DE Nichols It's always nice to have a wife who shares your interests especially if she willing to take care of the filming. And she can give some feedback during the filming to see maybe how other folks out there watching the video may be wondering about too. Thanks DE...
stuzman52 Your welcome and thanks are to you as well. I see I'm not the only one to make big comments to be sure my viewership fully understands. Thanks, teach, especially on Christmas. :) So on a rheostat still check the voltage as the PCM would, just realize it'll vary less. Did I get it now? lol
+DE Nichols Yes DE...just check the voltage as it will be a significant change in voltage. Remember, that the voltage will vary across a 40 - 250 ohm resistance. So, the voltage will vary from 0.7V to 2.5V across the fuel sending unit. There is enough variation in voltage that you can see a difference. So, are the kids at your house all excited about their gifts? Around here, it's a little quiet as my kids are all grown now...
When I unplug the wire from the pump the fuel gauge stays on empty, and when I jump the plug the gauge still stays on empty, any idea what could be wrong?
Hello man, i love your videos and i have one question please. I have a 2002 gmc envoy and the issue i am facing is that the fuel gauge is working inversely, means that when i full up my tank it goes all the way down and the orange led just lights up, and when fuel amount decreases it starts to go up until reaching full when the tank becomes empty. Thanks a lot 🙂
Hi Michael and glad to hear that you like the videos. The only thing that I believe that can cause this is that the wires to the fuel sending unit are reversed. For this to happen, the wires were cut possibly and a pigtail connector was installed. During installation, the wires were reversed by accident. More than likely the fuel sending unit and or pump was replaced in the past. I would start looking there at the tank to see if that's the case. Good luck Michael!
@@stuzman52 actually i have been facing this for a long time and i thought that replacing the sending unit may fix it, but few days ago i had to replace the whole fuel pump including the sending unit and i was shocked that nothing have changed
@@michaelsaleh55 While you were in there, did you see any signs of taped or spliced wires for the sending unit. Having reversed wires is the only thing that could cause this. Keep in mind these two wires could be swapped anywhere from the tank to the instrument cluster. As a test, you could reverse these wires and see what happens to the fuel gauge.
I have a 92 chevy k1500 that has been an ongoing saga. I bought it as a project and it has come a long way but still has bugs to be worked out, it surges on idle, sometimes badly then when it warms up goes into high idle. no check engine codes. things ive done are replace coolant temp sensor, rebuilt throttle body, checked egr valve, checked pcv valve, cleaned Iac motor, refreshed distributor, put new battery, tested with different ingnition module. timing is good, I adjusted valves and wires rotor and cap are all good. no arcing. I feel like it is a sensor problem because the computer seems to try to do corrections almost constantly, until it warms up and goes into closed loop, then it just sits on high idle. I check for vacuum leaks, and replaced the throttle body gasket when I rebuilt the throttle body. fuel is good. injectors seem to be spraying fine. I have a feeling it may be the IAC motor because the problem is intermittent, sometimes it starts and idles just fine. I dont have an oscilliscope so im kind of tapped out on things to try.
texas tough If you have a scanner that reads data, you could take a look at fuel trims to see how they are doing. My next suggestion would be to take a scope and see how the IAC is doing. Since you’ve checked everything else, you could try the IAC but keep in mind that it’s only a guess without the equipment to check it.
thank you im a retired HVAC contractor and major appliance tech, Ive always believed to fix something you must know how it works to begin with. from what im gathering, it seems besides initial timing the only thing that controls open loop idle is the coolant temp sensor and the IAC. so being the temp coolant sensor is new, and is working(if I unplug it throws a check engine light immediately), im leaning towards a intermittently failing Iac. as I said, sometimes we think we got it fixed, truck idles beautifully, then starts hunting again. after rebuilding the throttle body, it ran great, but I had removed the IAC to clean the throttle body, then replaced it. just touching the pintle could have unstuck it , then it stuck again. from what ive learned. the truck doesnt open the throttle plates at all during idle.. when the throttle plates are opened for acceleration IAC is closed, and ECM sees the TPS position, to advance timing, and increase fuel.. also do you think it matters which wiring harness goes to the injectors.. can they be swapped?
all I have is an OBD2 scanner, and the check engine lights dont tell very much for fine tuning these trucks. I may invest in a oscilliscope soon. my truck doesnt have a tach either, so that makes troubleshooting tougher too.
@@randy1ization Welcome to the retirement world Texas as I'm retired myself :) You are correct that the secret to troubleshooting is to understand how it works and from there you can develop your own strategy in troubleshooting. Here's a little background on the IAC on your vehicle. The IAC uses a stepper motor to control a pintle position which allows more or less air into an opening. At idle, the throttle valve would be closed, but the IAC will retract its pintle off of a seat in the throttle body to allow more air for idling. As you're crusing, the pintle would still be retracted off of its seat even though the throttle valve will be held open. The reason is so that when you lift your foot off of the accelerator, there will still be air going into the engine from around the pintle into the seat to prevent the engine from stumbling. Other areas where the idle would change is when you turn on the AC or when you turn the steering wheel and the line pressure increases in the power steering system. For those conditions, the idle speed would increase. These different positions of where the pintle moves in and out could be observed on a scanner that supports data which would be shown as IAC pintle counts. As the counts go up, the pintle would retract allowing more air into the engine. And as the counts go down, the pintle would extend blocking off air going into the engine. The PCM controls all four pulses through four transistors feeding the two windings going to the stepper motor. Although a scope is best to see these square wave signals, in a pinch you could use a test light if you want to verify them by its switching action I'll post a video where a procedure is shown for that at the end of this comment. Another test would be to lightly tap the IAC and see if the idle speed changes. If so, change the IAC as I wouldn't bother cleaning them as I haven't had much luck with that and they're not that expensive. Be sure to clean any carbon around the seat that the pintle sits in. With all that you've done, it's probably a bad IAC motor. Good luck on what you find and it's a good idea for a scope as they've come down a lot in prices. And they can take a lot of guesswork out of troubleshooting. You could look into Rigol and Hantek as most people seem to be satisfied with them and the price is not too bad. Here is the link to the video that I mentioned earlier. Although they're using a later model Buick, the IAC should be the same as on your vehicle. ua-cam.com/video/qMAUBU-6ErY/v-deo.html
Good job! sir, i guess you made a slight mistake. For half reflection your result should be 255 which is 2^8 (8 bits), 0 - 255 ; if your starting point( 0-point) is 40; you should subtract 255 - 40 =215 then divide it to 2 = which is 107.5 + half of your 40 =20 then 107.5+40 = 157.5
Terry, Your wife is a Angel, how do you get her to take such an interest in something that my wife would probably fall a sleep listening to. If I ever explained something in that much detail on a white board to her, she would probably hit me over the head with it ! LOL ! Only kidding, the vid was great, can't wait for part 2 !
+Billy R Hi Billy...yes, she is a great lady and is always there for me when I need some help. As you've mentioned, most ladies couldn't give a hoot about all this stuff, but she seems to take somewhat of an interest in it. It could be that she knows to pay attention because I have been known to ask her questions. Maybe she don't want to be embarrassed on camera LOL...thanks for watching Billy!
Richard. I don't have a channel, that's just Steve Rob, who is a good friend of mine, talking about my future channel that I don't have ! LOL! Thanks for asking !
Terry, thanks for making this very educational video.
Thank you Kenny and have a great day!
Nice intro / refresher! Props to your wife for asking questions! A lot of things in school didn't make sense to me (due to the language barrier in the early years of moving to Canada)... and I was always too chicken to speak up to ask for clarification (would not have been cool I thought). I'm still the quiet type... but thank goodness for the internet, youtube & all the great channels that I can refresh & learn from. Thanks Terry!
+Thomas EXOVCDS Always a pleasure Thomas and good to see your comment. And no need to be the quiet type as you're amongst friends and have a lot of knowledge to share yourself. Thanks for dropping in and sharing your thoughts!
Great video, you explain things really well, I am glad your back with you in depth diagnostic videos, thanks
+Jonathan Dean Thanks Jonathan, I appreciate it and thanks for leaving a comment!
Terry your tutorial videos are fantastic and your teaching manner is over the top. thank you for taking the time to post. Looking forward to seeing more. thanks again.
+George Heri Thanks George for the comment and I appreciate it...
Great video, explained to where it was easily understood !
Enjoyed the video Terry. Very well explained.
+White Tiger Thanks White Tiger as I appreciate it. And thanks for dropping in and leaving a comment!
Hi Terry. I found you again after a google search, to decide whether my occasionally unreliable dashboard fuel gauge was the dash stepper motor or the sending unit inside the tank. As always, I like your clear thinking. Of course dealing with an intermittent problem can be frustrating. I will attach my scan tool, make a baseline plot plot of fuel gauge voltage reading when the gauge is working, then wait for a convenient time when it fails. Then when the dash shows a bad reading, I'll use the scan tool to decide whether the stepper motor is accurately representing the voltage coming from the sending unit. I suspect the sending unit is on its way out, but a stepper motor would be so much easier to swap out, ha ha.
I like the way that you think too and your method should be able to decipher whether it's the stepper motor or the sending unit.
Your videos are terrific. Love watching them. Best electrical videos I have come across. Maybe you can explain what a pull up resistor does inside the PCM in one of your videos.
Thank you Arthur and glad you like the videos. Another one to add to this list of videos :) Have a good one!
Excellent video. My son has a 2006 Chevy Silverado with a P0449 evaporative emission vent solenoid control circuit, and a p0463 fuel level circuit sensor one high voltage. Could the p0463 fuel level circuit code be causing the P0449 evaporative emissions code?
More than likely you have two separate issues. The P0449 is telling you that you have a circuit issue with the vent solenoid. The solenoid could be open, wire broke or not likely an ECM issue. And the fuel level sending unit is a common issue on GM issues where the fuel sending unit is the most likely cause.
@@stuzman52 Thanks.
Hello Mr. Stuzman! What output signal does an auxiliary antifreeze cooling pump have on Volkswagen cars?
I wouldn't have a clue for an answer. I suspect that you would have to look into the service info for that. Have a great day!
@stuzman52 ok! Thank you Mr Stuzman!
congratulations, very good information
Thank you very much Chevy 51.
great info how would I diagnose a system that uses two sending units
I've never worked on one Paul, but if you have two fuel tanks, I would assume that you check each sending unit individually.
Nice- very good level of understanding for someone to begin their repair with. Terry I always found the words "infinite resistance" perplexing , is there any difference than as in a "open circuit" ?
+Steve Rob Means the same thing Steve. Probably would have been better to just say open...
very interesting video...here comes the question and let me first begin with i have purchased many voltage testers that have all rusted in my tool box cause i never learned how to use them lol..Since the ohm calculations are so precise on the level of a empty to a full tank of gas why do i get better gas mileage on the first half of the tank than the second half when the needle goes the same amount of distance on the gauge?? thanks Terry
+RICKAFIX Hey Rick and hope you're doing well. Your gas mileage should be the same throughout although the rate of decline for the needle on the gauge could vary. As one viewer pointed out, the different configurations of fuel tanks could cause this. In this video, I was thinking more of a fuel tank that was symmetrical in depth. In the second video, I'll cover the different tank configurations and how this could vary the needle which may not be linear. Take care Rick...
When filling the tank the resistance of the resistor is varies bec of the movement of the float causing the resistance to change im i right sir
Yes, you are correct!
My car, Civic Es 8 has a problem of indicating a wrong fual level.when i stop the vehicle with some amount of fuel it indicates correctly on my instrument cluster gauge. But next day when I start the car, the fuel level seems to go down suddenly.After driving 15 to 20 mins, it goes up again like it shows before, this happened after i changed my fual pump with floatr, could you please help me on this??
My best guess is that you have an issue with the fuel sending unit. As you said, the problem appeared once you changed the fuel pump and sending unit.
Sorry i dont know what is the sending unit of my fual pump, can you please explain to me this with a picture ??
Also please let me know can i change only sending unit instead of changing fual pump,
OH, so on a rheostat, if I was looking at volts I might see very little change and think the component was bad, but knowing some are rheostats, I should look at the amps and see the great variation. I just learned something new. Did I get it right?
For when I paid attention and counted your angel and I are both 1 for 2 for answered questions correctly. :)
+DE Nichols Hi DE...when one speaks of a rheostat, it's more of how it's wired as I point out in the videos which is more of varying current. The potentiometer where it's name is potential, (voltage), varies voltage. With a potentiometer, the current wouldn't vary through the total resistance of the pot as its resistance is fixed even if you were to move the wiper. Yet, the voltage will vary from one of the outside legs to the wiper. When you see a pot wired with its wiper connected to one of the outside legs, like fuel sending units, folks in the industry will say that its a rheostat which would vary the current, but at the same time it will vary the voltage too because the total resistance of the rheostat will change because the wiper is part of the function now. Even still, the computer is still looking at a voltage change. You could see the variation in current, but it would be an extra step to wire an ammeter in series with it. I would just measure the voltage across the sending unit as I show which is faster. Thanks for leaving a comment DE!!!
+DE Nichols It's always nice to have a wife who shares your interests especially if she willing to take care of the filming. And she can give some feedback during the filming to see maybe how other folks out there watching the video may be wondering about too. Thanks DE...
stuzman52
Your welcome and thanks are to you as well. I see I'm not the only one to make big comments to be sure my viewership fully understands. Thanks, teach, especially on Christmas. :)
So on a rheostat still check the voltage as the PCM would, just realize it'll vary less. Did I get it now? lol
+DE Nichols Yes DE...just check the voltage as it will be a significant change in voltage. Remember, that the voltage will vary across a 40 - 250 ohm resistance. So, the voltage will vary from 0.7V to 2.5V across the fuel sending unit. There is enough variation in voltage that you can see a difference. So, are the kids at your house all excited about their gifts? Around here, it's a little quiet as my kids are all grown now...
When I unplug the wire from the pump the fuel gauge stays on empty, and when I jump the plug the gauge still stays on empty, any idea what could be wrong?
Will Snow get a resistor about 250 Ohms and put that across the plug. You should get a full tank reading.
Hello man, i love your videos and i have one question please.
I have a 2002 gmc envoy and the issue i am facing is that the fuel gauge is working inversely, means that when i full up my tank it goes all the way down and the orange led just lights up, and when fuel amount decreases it starts to go up until reaching full when the tank becomes empty.
Thanks a lot 🙂
Hi Michael and glad to hear that you like the videos. The only thing that I believe that can cause this is that the wires to the fuel sending unit are reversed. For this to happen, the wires were cut possibly and a pigtail connector was installed. During installation, the wires were reversed by accident. More than likely the fuel sending unit and or pump was replaced in the past. I would start looking there at the tank to see if that's the case. Good luck Michael!
@@stuzman52 actually i have been facing this for a long time and i thought that replacing the sending unit may fix it, but few days ago i had to replace the whole fuel pump including the sending unit and i was shocked that nothing have changed
@@michaelsaleh55 While you were in there, did you see any signs of taped or spliced wires for the sending unit. Having reversed wires is the only thing that could cause this. Keep in mind these two wires could be swapped anywhere from the tank to the instrument cluster. As a test, you could reverse these wires and see what happens to the fuel gauge.
@@stuzman52 i will try this, thanks a lot 🙂
@@michaelsaleh55 You're welcome. Good luck!
I have a 92 chevy k1500 that has been an ongoing saga. I bought it as a project and it has come a long way but still has bugs to be worked out, it surges on idle, sometimes badly then when it warms up goes into high idle. no check engine codes. things ive done are replace coolant temp sensor, rebuilt throttle body, checked egr valve, checked pcv valve, cleaned Iac motor, refreshed distributor, put new battery, tested with different ingnition module. timing is good, I adjusted valves and wires rotor and cap are all good. no arcing. I feel like it is a sensor problem because the computer seems to try to do corrections almost constantly, until it warms up and goes into closed loop, then it just sits on high idle. I check for vacuum leaks, and replaced the throttle body gasket when I rebuilt the throttle body. fuel is good. injectors seem to be spraying fine. I have a feeling it may be the IAC motor because the problem is intermittent, sometimes it starts and idles just fine. I dont have an oscilliscope so im kind of tapped out on things to try.
texas tough If you have a scanner that reads data, you could take a look at fuel trims to see how they are doing. My next suggestion would be to take a scope and see how the IAC is doing. Since you’ve checked everything else, you could try the IAC but keep in mind that it’s only a guess without the equipment to check it.
thank you im a retired HVAC contractor and major appliance tech, Ive always believed to fix something you must know how it works to begin with. from what im gathering, it seems besides initial timing the only thing that controls open loop idle is the coolant temp sensor and the IAC. so being the temp coolant sensor is new, and is working(if I unplug it throws a check engine light immediately), im leaning towards a intermittently failing Iac. as I said, sometimes we think we got it fixed, truck idles beautifully, then starts hunting again. after rebuilding the throttle body, it ran great, but I had removed the IAC to clean the throttle body, then replaced it. just touching the pintle could have unstuck it , then it stuck again. from what ive learned. the truck doesnt open the throttle plates at all during idle.. when the throttle plates are opened for acceleration IAC is closed, and ECM sees the TPS position, to advance timing, and increase fuel.. also do you think it matters which wiring harness goes to the injectors.. can they be swapped?
all I have is an OBD2 scanner, and the check engine lights dont tell very much for fine tuning these trucks. I may invest in a oscilliscope soon. my truck doesnt have a tach either, so that makes troubleshooting tougher too.
@@randy1ization Welcome to the retirement world Texas as I'm retired myself :) You are correct that the secret to troubleshooting is to understand how it works and from there you can develop your own strategy in troubleshooting. Here's a little background on the IAC on your vehicle. The IAC uses a stepper motor to control a pintle position which allows more or less air into an opening. At idle, the throttle valve would be closed, but the IAC will retract its pintle off of a seat in the throttle body to allow more air for idling. As you're crusing, the pintle would still be retracted off of its seat even though the throttle valve will be held open. The reason is so that when you lift your foot off of the accelerator, there will still be air going into the engine from around the pintle into the seat to prevent the engine from stumbling. Other areas where the idle would change is when you turn on the AC or when you turn the steering wheel and the line pressure increases in the power steering system. For those conditions, the idle speed would increase. These different positions of where the pintle moves in and out could be observed on a scanner that supports data which would be shown as IAC pintle counts. As the counts go up, the pintle would retract allowing more air into the engine. And as the counts go down, the pintle would extend blocking off air going into the engine.
The PCM controls all four pulses through four transistors feeding the two windings going to the stepper motor. Although a scope is best to see these square wave signals, in a pinch you could use a test light if you want to verify them by its switching action I'll post a video where a procedure is shown for that at the end of this comment. Another test would be to lightly tap the IAC and see if the idle speed changes. If so, change the IAC as I wouldn't bother cleaning them as I haven't had much luck with that and they're not that expensive. Be sure to clean any carbon around the seat that the pintle sits in. With all that you've done, it's probably a bad IAC motor. Good luck on what you find and it's a good idea for a scope as they've come down a lot in prices. And they can take a lot of guesswork out of troubleshooting. You could look into Rigol and Hantek as most people seem to be satisfied with them and the price is not too bad. Here is the link to the video that I mentioned earlier. Although they're using a later model Buick, the IAC should be the same as on your vehicle. ua-cam.com/video/qMAUBU-6ErY/v-deo.html
Good job! sir, i guess you made a slight mistake. For half reflection your result should be 255 which is 2^8 (8 bits), 0 - 255 ; if your starting point( 0-point) is 40; you should subtract 255 - 40 =215 then divide it to 2 = which is 107.5
+ half of your 40 =20 then 107.5+40 = 157.5
Terry, Your wife is a Angel, how do you get her to take such an interest in something that my wife would probably fall a sleep listening to. If I ever explained something in that much detail on a white board to her, she would probably hit me over the head with it ! LOL ! Only kidding, the vid was great, can't wait for part 2 !
+Billy R Hi Billy...yes, she is a great lady and is always there for me when I need some help. As you've mentioned, most ladies couldn't give a hoot about all this stuff, but she seems to take somewhat of an interest in it. It could be that she knows to pay attention because I have been known to ask her questions. Maybe she don't want to be embarrassed on camera LOL...thanks for watching Billy!
God Bless !
Billy R what is the name of your channel
Richard. I don't have a channel, that's just Steve Rob, who is a good friend of mine, talking about my future channel that I don't have ! LOL! Thanks for asking !
Lol
Just wish all cars had a access panel to get to the sending units, with out dropping the tanks . A lot of rusty tanks around here
+wtbm123 Would be nice Terry if they all had that.
Please draw a blown up version showing all the parts in large it's not helpful when it's small
Quem é brasileiro e estar tentando entender