Thank you so much for your video and explanation! I'm 32 years old and honestly thought I'd never understand things like this in such detail. I suppose it really does just take the right teacher with the right method. Thank you!
Even the seemingly complicated stuff is nothing more than blocks of simpler things put together. Break down the simple things and it's not that hard to understand.
Thanks Steve. I knew the video would be a little long, but I wanted to get everything covered so guys could troubleshoot these systems with no problems.
HI Tito...Yes, I remembered when you subscribed and thank you. Hopefully, the video made some sense to you, and glad to hear that you didn't think it was to long.
Robert Parker you're quite welcome Robert and hope the video helps you in your troubleshooting. The ECT circuit is one of the simplest circuits to troubleshoot. You shouldn't have any problems in finding your issue and I'm sure that all would be well. 👍
This is a fantastic video with great explanation. Thumps up. I have subscribed. Your camera person is doing an excellent job. Will be happy if you can explain how the circuit works on a Hot Wire Mass Air Flow Sensor. Looking forward to your next video. All the best.
Kenny Doolarchan Thank you very much Kenny and glad you liked the video. I was thinking of some engineering videos of how things work so stay tuned for that. And all the best to you also. 😀👍
that is awesome teacher. many thanks for sharing!!!!! I am a process engineer but I do love cars.... I also love the theory and i was trying to figure out the functioning of this until i got your video. greetings from Venezuela!!!!
Luis Ledezma thank you very much Lewis and glad to hear that you found the video helpful. You can check out some of my other videos as I've done a few on electronics theory. Have a great weekend!
Hi Michael. Yeah, I was worried about the length of the video that most people wouldn't watch it. Glad to hear that you thought the length was okay. I could have made it longer by explaining how the computer takes a voltage reading and translates it to temperature. But since that was more of an engineering situation and the video would get even longer, I decided not to include that. Thanks for your comment and for taking the time to watch the video.
Thanks! I'm looking at one at the moment so now I've got a clear idea of what I'm looking at. I'm only getting 3.2 volts with the connector disconnected.
Excellent that you understand the circuit operation. Sounds like you've got another sensor that's shorted which is pulling your 5V reference down. Worse case scenario is that the issue is inside the PCM; hopefully not though.
Hey Mike, (if I remember you correctly from Autonerdz), and hope you're doing well. Glad you liked the video and looking forward to other videos from you. Take care and don't work too hard...
Thanks stuzman, unfortunately I'm quite the work aholic, lol. I took on a part time job instructing at the local Community College teaching intro to Electrical for the Diesel Program. I'm extremely busy but I am enjoying it. What have you been up to?
busjockey1 Wow, workaholic and good for you that you're doing some teaching at the local college. I'm trying to find ways to slow down a little (smiling). Pretty much the same as you busjockey, trying to make a living and keeping my head above the water. Have a good one and keep those students in place.
Thanks again, I thought it was looking like another sensor, the reason I was watching your video was to see if it could have been a short to earth but from your video and other things I've looked at seems like I would have 0 volts. I think the fault I had was short to earth on the scanner but someone else at work cleared it. It's not my car anyway, it came in for a thermostat housing and now it won't start 😂
just a thought on ect circuit. I measure 5.00v source on my car temp sensor circuit.. I"m guessing that if I use a variable resistor pot as the temp sensor and get an output of 2.5v that will tell me the value of the internal resistor used in the ecu/ecm, or close to it probably. Might lead to a way to be able to check if the internal resistor is ok. another note in my case using forscan obd software, I can see the voltage and temp computer is seeing in real time, my issue is the voltage goes along normal for a minute or two while coolant is cold( somewhere around 1.5v or so), and then it shoots upward to 4.17volts (off scale: high), it is a clue to what my problem is, but identifying why it shoots up all of a sudden is still unsolved ( working on it). Once the voltage has shot up out of range, if I disconnect the temp sensor lead and put it back on, the voltage reads normal voltage ( 1.5v approx), but within a fraction of a second it goes high voltage again ( 4.17v). That also is probably some clue to what is happening, some sort of short I"m guessing. At the moment I"m guessing its in the temp sensor, some internal connection to the thermistor that is broken but at low temps makes good enough connection. Thinking I will use a 20k pot to replace sensor( as sensor reads about 20k when cold) and see if it stills shoots up after engine warms a bit.
Sounds like you've been doing a little thinking which is good! Yes, you can use a variable resistor as you've said and if you get 2.5V across it, measure it's resistance, then you'll know the internal resistance where they will be equal. One thing that I didn't show in the video is that some ECT circuits will use stepped resistors or even a different voltage value than 5VDC. Try plotting out the temperature of the ECT over time from cold to hot and see what it looks like. It's possible that the graph would become more normal as the temperature gets hotter. Take a look at this article and you'll see what I mean about stepped resistors and different voltage values. Your car may have this type of circuitry for the ECT circuit. bccskillsusa.weebly.com/uploads/4/3/3/2/43327659/el2.sensors.pdf
@@stuzman52 Once again excellent information, thankyou! I have looked over the article and understand, I will do some testing and try nut this out. Its quite interesting stuff. My ecu is reading low volts ( approx 1.5v) for cold engine, then rapid ( instantaneous) change to 4.17v after a minute or so of engine running. So I guess the computer is thinking your engine goes from hot/warm when first started, to screaming cold instantaneously after a minute or so.........no wonder it gives an error....p0118 code...high volts when its probably expecting low volts. The sensor itself appears to give high resistance at cold engine ( 20k or so) and decreases as engine warms up, about 2.5k with no fans on, after a 10min drive. So sensor 'appears' ok at this stage. The plot thickens. Will do some tests with suitabe variable resistor next, it might give a clue to the problem.
@@namenotshown9277 Glad to hear that the article helped you out. Always good to have the most information available. I'm sure that you'll get it figured out and using a variable resistor will surely give you some insight into the issue. Good luck!
I'm getting 5 volts on one of the wires, but then I take off the Sensor and run a paper clip to it, it's reading N/A on my scan tool. So does that mean I'm not getting ground? Maybe my ground wire is short? Because my cooling fans aren't turning on at all. I'm measuring 5 volts. And when I have it plugged in and engine turned on with a scan tool I'm reading around 1.5-3.2 volts. It drops down to 1.3 ish when the engine is hot. But still my fans won't turn on. I'm guessing it's the ecu ground?? I'm not even sure anymore! I'm confused. You didn't mention in the video about what would happen if the ground wire is short! Please help explain it to me. Thanks
Hi Scott! With the sensor disconnected, you would see 5V as you've mentioned. With the sensor disconnected, and with a jumper across the harness, (going back to the computer), the computer would see near 0V which would indicate a very hot condition. You're saying that your scanner says N/A which I would assume means Not Applicable. This isn't correct. See what your voltage says. With the sensor plugged in, you're seeing a voltage reading from 1.5-3.2V which sounds correct. And when the engine is hot, you read about 1.3V which again sounds correct. Are you getting a code for the ECT sensor? And if your coolant fans aren't coming on, then I would suspect that you have an issue with the coolant fan(s) circuitry.
Thanks for the subscription. You say my thermistor is broken and want to know that thermistor detail. You'll have to be more specific as in how is the thermistor broken; open, skewed, etc.
@@stuzman52 i use airflow 449 from mitsubishi but inside my thermistor is broken.. so i want to replace to the new one, but don't know the detail of the thermistor.
Ok I understand so if the engine is cool the iat sensor read high voltage so the the fuel ratio burn a little rich and when the engine is warm up the voltage drop and engine fuel ratio go down so the engine sound goes down ok and the map read the same air intake as well as the 02 sensor right
You are correct with the IAT as it will make small adjustments to the air/fuel ratio. The ECT will make larger adjustments to the air/fuel ratio. I believe the IAT is used mainly for measuring the temperature of the air coming into the engine to know the weight of the air. As for the MAP and O2, these two sensors measure the intake vacuum to determine the load on the engine, (again for air/fuel ratio) and the O2 sensors are used to determine the amount of oxygen in exhaust to again fine tune the air/fuel ratio.
Another great video. Thank you. I would appreciate if you could kindly explain the reason for the following hypothetical scenario. Say a fuse was continually burning out after being replaced. Say the circuit was for the left front headlamp. Say there was a short where a wire in the circuit became exposed and was rubbing against the metal body of the car. My question is this: What could be an explanation why the short would cause the fuse to burn out? Thank you
Thank you toyo for the comment on the video. With all circuits, there must be a load. Think of the load as what's doing the work and of course with all loads, there is resistance or the property which impedes the flow of electrons. Let's use conventional current flow for this example, although we know that electrons actually travel from the negative side of the battery to the positive side. Electrons leave the positive post, goes through a fuse, switches, relays, etc. and finally out to the load. These electrons will travel through the filament, (there's our load and resistance) and then make their return trip back to the negative side of the battery. As you may know, the negative side of the battery is connected to the engine block, chassis and to the sheet metal of the car. Think of all these things as the negative side of the battery. So, when electrons leave the negative side of the battery, goes to the metal chassis where the B+ shorted wire is, we bypassed the load which means very low resistance to the flow of electrons. And that's when the fuse blows. Another way to think of this is to imagine that we took a wire and jumped directly across the battery posts. This will create the maximum current flow out of the battery since we don't have any resistance, (load) to impede those electrons. The reason we have fuses in circuits is to protect the wiring. And each wire size is rated for a safe maximum number of amps. Hope that helps you out toyo.
Hey stutzman question . The two wires going to my iat has 5v across it . But the scanner is seeing 0volts on the display and -198 degrees . This is anew pcm and a new iat sensor , neither the older new iat show a resistance value when I check them directly. I checked continuity of both wires going to and back from pcm to iat . Both check good . I am at a loss . Same thing with old pcm it’s a 1994 dodge Dakota 3.9 mpfi if that matters. If you can steer me correct I would appreciate it . Thanks again
Blinded By The Light That’s very interesting as I’ve never ran across one like that. That’s probably how it works, and you could check with your service literature to be sure,
Can I get your opinion on some live data i'm seeing ( if you have time!) With obdii scanner looking at live data for voltage and temp of ect ( degree celcius down here used). I get good data as engine warms up, gets to 60 degC and voltage jumps from 1v up to 4.23v. It does this everytime, so I assume its the second resistor or similar turning on. Now it gets weird: The engine temp live data continues to be accurate and changes as it should ( fans kick in at 80deg), but the voltage graph on live data shows constant 4.23v no change over time. At the same time I"m looking at voltage across ect using voltmeter and it shows voltage is changing not constant. So computer knows what is correct engine temp, but its voltage output on live data stays at 4.23v ( until engine goes under 60degC and it jumps back to just one resistor. I swap ecu......same thing. any thoughts on that one?
I'm assuming that this is normal operation for your vehicle especially since you changed the ECU and it's doing the same thing. If you have the service literature, it may even mention the operation of the sensor which I suspect that it's switching in the second resistor inside the ECU. If you don't have any issues with the car and it doesn't give a code for the ECT, I wouldn't worry about it.
@@stuzman52 thanks for reply, it is good to know the car is reading correct temp, even though on the obdii live data the voltage for temp is not coreect on second resistor. I'm sure it will lead to solution eventually but for now car is fine as is. appreciate your video very helpful indeed
That 5V reference seems to be used in all kind of sensor circuits. One thing I've noticed this past decade when my battery is failing (on many different vehicles now) is a sag in idle speed. My theory is that at slow idle my alternator is unable to keep base voltage up, and that translates into a sag in the 5V reference baseline. That sag seems to allow idle to drop, without the usual automatic correction from the PCM. With a little gas and some time for the alternator to recharge a failing battery, all is well. I haven't come across a better explanation -- any thoughts?
Hey Dave. You always give me these thought provoking questions (smiling)... Your theory sounds good, but there is one flaw that doesn't make sense. I can't say for sure what the part number is for the voltage regulator inside the PCM, but all regulators that I've run into needs at least a couple of volts above it's output voltage for the output voltage to stay stable. I looked up the data sheet for the 7805 regulator and it can maintain a +5VDC output where the input voltage can vary from 7V-35V. So, even when the battery is failing, the 5V should still be constant. I can't explain that when the battery is failing, why does the idle speed drop, unless there are other things going on such as bad connections at the battery or some other place. I could see that if the generator was failing such as having a bad diode that AC voltage could get on the DC bus line. And with that scenario, all kind of things would be possible and not just with the idle speed. I'll have to think about it some more Dave. Good question though, and thanks for dropping in and taking the time to comment and for watching the video.
If your reference deviates away from whatever that voltage should be then you've got a problem. Reference voltage is supposed to be the one stable constant for all of your sensors. My problem with your theory is that the alternator should be putting out about 12-14v minimum right? Using a resistor it drops to reference voltage (4.5-5.0 most cases). So it shouldn't negatively affect the reference circuit in anyway unless system voltage drops to below 5 volts. Your car isn't going to stay running with such low system voltage anyway so in that regard the problem would obviously be the alternator. Reference voltage is usually provided by a pin from the ECU. You can probe the reference circuit directly at the ECU and look for deviations there. Reference voltage shouldn't have anything to do with the alternator unless it's an obviously malfunctioning alternator (which should be obvious due to poor battery+ voltage)... both for total voltage and stability of that voltage.
I was surprised the first time this happened, after a parking lot boost 10 years ago. I couldn't maintain idle without goosing the throttle. But after a few minutes of driving, no problem. An alternator needs to be spinning at a minimum rate to generate power, which is why I'm thinking that voltage is sagging at such low (~300/min) RPM. Of course when this happens in a parking lot you don't have the arms or tools to do diagnostics. I just know the problem resolves after a few minutes of recharging with engine on.... This has happened with three different vehicles now, it's becoming a recognizable pattern. Any ideas?
spelunkerd For my vehicle anything under 500 RPM and it will begin to stall. How are you not stalling under 300 RPM? That's my cars starter speed. High lift cams? Sounds like a bad alternator to be honest. Are you using some kind of inverter on these vehicles. There has to be a common denominator. Something electrical you are introducing into the 3 cars that is drawing electricity. Parasitic drain perhaps? Nothing should mess with that 5v reference because it comes from inside the ECU itself. The resistor is inside the ECU then pins out to specific wires. Also the reference voltage has a ground circuit that it might monitor going into the ECU too. 1 or multiple pins for reference voltage out and reference ground in.
keith farrell Hi Keith. I'm a little busy with a lot of other things, but do see some more electrical related items coming up in the near future. So, stay tuned.
I have ect volt high code p0118, been trying to solve the puzzle for a couple of weeks now, this is one damn excellent video on understanding ect ( or iac etc), much appreciate your posting it. I'll keep working on my problem till I solve it, this info will be extremely helpful. One thing I dont understand is why there is an internal earth? I assume its different to the chasis or battery earths though connected in some way. Just by way of example lets say you use chasis earth instead of internal earth for example in video, what would be the outcome?
Glad to hear you're finding the video helpful. The internal ground inside the PCM is to reference the 5VDC for the reference voltage which is used for the ECT or IAT circuits. It's possible that you can connect the external battery ground, but more than likely it's isolated. The reason is that the battery ground will have a lot of voltage spikes on it from all of the accessories on the car such as coils, motors, solenoids, etc. When checking the ECT or IAT circuit, it's best to use the internal ground for these circuits as the signal will be cleaner especially if you're using a scope to look at the signal over a period of time. You could try referencing the battery ground for these circuits with your voltmeter to see if you will get a voltage as some systems may have the external ground connected to the internal ground. Good luck on finding your issue!
@@stuzman52 thanks so much for informative reply, car is ford falcon au ( 1999), very common car here in australia, amazingly reliable cars but getting a bit old now.
stuzman Yes, of course, thanks so much! I was referring to the computer reading a voltage equivalent to cold temperature and enriching the mixture as a result hence vehicle would run properly when cold and verify there was something wrong with the IAT. Am thinking of this also a way to test the IAT if no voltmeter was available and vehicle only ran rough when cold. Just a thought. TX again!
Roberto Santiago Rodriguez Zig If you unplug the connector the computer would see 5VDC which the computer would interpret as-40F/C. While the connector is pulled off, you could place a jumper across the two terminals. The computer would see this has 0 VDC. The computer would see this as a very hot condition. These two tests are used for circuit operation and wiring integrity. You could monitor the PID to see how the computer responds.
I did it, I disconnected the IAT sensor on my 1995 F150, 5.0 liters 2wd, automatic and the truck drove definitely better while cold. Of course, the PCM was smart enough to know it wasnt -40 degrees Fahrenheit outside so it turned on the Check Engine Light. It must have been using a low temperature parameter because the subsequent enrichment of the mixture to compensate for cold air, caused the engine to no longer run lean and got rid of the hesitation and lack of power. Temperature outside was actually 78 degrees Fahrenheit; hope it helps someone. Thanks again Stutzman for your explanation.
Thank you so much for your video and explanation! I'm 32 years old and honestly thought I'd never understand things like this in such detail. I suppose it really does just take the right teacher with the right method. Thank you!
Even the seemingly complicated stuff is nothing more than blocks of simpler things put together. Break down the simple things and it's not that hard to understand.
a very good explantation better than my professor's explanation BACK IN the university. I hope you doing well sir .my salutation to you
Thank you Peter and glad you liked the video. Have a great day!
Seriously, down to earth,explanation of the workings of a ntc circuit.
+Tom OConnor Glad to hear that you liked the video Tom.
Awesome technical explanation. Please continue the similar teaching way.
Thank you selvam and will do some more in the near future.
Fantastic - understood it all - was a bit too short - I think you covered it all. Thanks !!
Thanks Steve. I knew the video would be a little long, but I wanted to get everything covered so guys could troubleshoot these systems with no problems.
I watched your video at midnight and didn't think it was to long thanks for your time. (I'm a subscriber too)
HI Tito...Yes, I remembered when you subscribed and thank you. Hopefully, the video made some sense to you, and glad to hear that you didn't think it was to long.
This is a great video. I'm in the process of troubleshooting an ect sensor and find this video and your knowledge a great help! Thanks!!
Robert Parker you're quite welcome Robert and hope the video helps you in your troubleshooting. The ECT circuit is one of the simplest circuits to troubleshoot. You shouldn't have any problems in finding your issue and I'm sure that all would be well. 👍
This is a fantastic video with great explanation. Thumps up. I have subscribed. Your camera person is doing an excellent job. Will be happy if you can explain how the circuit works on a Hot Wire Mass Air Flow Sensor. Looking forward to your next video. All the best.
Kenny Doolarchan Thank you very much Kenny and glad you liked the video. I was thinking of some engineering videos of how things work so stay tuned for that. And all the best to you also. 😀👍
Strongly agree with your suggestion, Thank you for bringing it up.
Great electrical lesson on thermistor design and ohms law.
Thanks DJ. Yeah, it was a probably a little long, but at least the info is there to help guys out during their troubleshooting.
that is awesome teacher. many thanks for sharing!!!!! I am a process engineer but I do love cars.... I also love the theory and i was trying to figure out the functioning of this until i got your video. greetings from Venezuela!!!!
Luis Ledezma thank you very much Lewis and glad to hear that you found the video helpful. You can check out some of my other videos as I've done a few on electronics theory. Have a great weekend!
Great explanation. Excellent. Not too long at all.
Hi Michael. Yeah, I was worried about the length of the video that most people wouldn't watch it. Glad to hear that you thought the length was okay. I could have made it longer by explaining how the computer takes a voltage reading and translates it to temperature. But since that was more of an engineering situation and the video would get even longer, I decided not to include that. Thanks for your comment and for taking the time to watch the video.
Thank you very much! Now i understand how it works.
Always glad to help Tomasz and also good to hear that you understand how it works. Also thanks for taking the time to drop by to watch the video.
Well explained and very nicely put together video, Thank you very much sir.
Thank you very much for the comment and dropping in!
The best explanation in the world thanks thanks thanks im from algeria country ❤❤❤
You are welcome!
Thanks! I'm looking at one at the moment so now I've got a clear idea of what I'm looking at. I'm only getting 3.2 volts with the connector disconnected.
Excellent that you understand the circuit operation. Sounds like you've got another sensor that's shorted which is pulling your 5V reference down. Worse case scenario is that the issue is inside the PCM; hopefully not though.
Good job stuzman, I couldn't have explained it any better. This video gives me an idea for a video. Later.
Hey Mike, (if I remember you correctly from Autonerdz), and hope you're doing well. Glad you liked the video and looking forward to other videos from you. Take care and don't work too hard...
Thanks stuzman, unfortunately I'm quite the work aholic, lol. I took on a part time job instructing at the local Community College teaching intro to Electrical for the Diesel Program. I'm extremely busy but I am enjoying it. What have you been up to?
busjockey1 Wow, workaholic and good for you that you're doing some teaching at the local college. I'm trying to find ways to slow down a little (smiling). Pretty much the same as you busjockey, trying to make a living and keeping my head above the water. Have a good one and keep those students in place.
Great explanation and thank you for taking the time hope the cold is better Regards Tom Aberdeenshire Scotland +++
Hey Mike and thanks! Yep, the cold is all gone now :)
Thanks again, I thought it was looking like another sensor, the reason I was watching your video was to see if it could have been a short to earth but from your video and other things I've looked at seems like I would have 0 volts. I think the fault I had was short to earth on the scanner but someone else at work cleared it. It's not my car anyway, it came in for a thermostat housing and now it won't start 😂
Glad to hear that you understand how IAT and ECT sensors work! I'm sure that you'll get it all figured out with the no start :)
just a thought on ect circuit. I measure 5.00v source on my car temp sensor circuit.. I"m guessing that if I use a variable resistor pot as the temp sensor and get an output of 2.5v that will tell me the value of the internal resistor used in the ecu/ecm, or close to it probably. Might lead to a way to be able to check if the internal resistor is ok.
another note in my case using forscan obd software, I can see the voltage and temp computer is seeing in real
time, my issue is the voltage goes along normal for a minute or two while coolant is cold( somewhere around 1.5v or so), and then it shoots upward to 4.17volts (off scale: high), it is a clue to what my problem is, but identifying why it shoots up all of a sudden is still unsolved ( working on it). Once the voltage has shot up out of range, if I disconnect the temp sensor lead and put it back on, the voltage reads normal voltage ( 1.5v approx), but within a fraction of a second it goes high voltage again ( 4.17v). That also is probably some clue to what is happening, some sort of short I"m guessing. At the moment I"m guessing its in the temp sensor, some internal connection to the thermistor that is broken but at low temps makes good enough connection. Thinking I will use a 20k pot to replace sensor( as sensor reads about 20k when cold) and see if it stills shoots up after engine warms a bit.
Sounds like you've been doing a little thinking which is good! Yes, you can use a variable resistor as you've said and if you get 2.5V across it, measure it's resistance, then you'll know the internal resistance where they will be equal. One thing that I didn't show in the video is that some ECT circuits will use stepped resistors or even a different voltage value than 5VDC. Try plotting out the temperature of the ECT over time from cold to hot and see what it looks like. It's possible that the graph would become more normal as the temperature gets hotter. Take a look at this article and you'll see what I mean about stepped resistors and different voltage values. Your car may have this type of circuitry for the ECT circuit. bccskillsusa.weebly.com/uploads/4/3/3/2/43327659/el2.sensors.pdf
@@stuzman52 Once again excellent information, thankyou!
I have looked over the article and understand, I will do some testing
and try nut this out. Its quite interesting stuff.
My ecu is reading low volts ( approx 1.5v) for cold engine, then rapid ( instantaneous) change to 4.17v after a minute or so of engine running. So I guess the computer is thinking your engine goes from hot/warm when first started, to screaming cold instantaneously after a minute or so.........no wonder it gives an error....p0118 code...high volts when its
probably expecting low volts.
The sensor itself appears to give high resistance at cold engine ( 20k or so) and decreases
as engine warms up, about 2.5k with no fans on, after a 10min drive. So sensor 'appears' ok
at this stage. The plot thickens. Will do some tests with suitabe variable resistor next,
it might give a clue to the problem.
@@namenotshown9277 Glad to hear that the article helped you out. Always good to have the most information available. I'm sure that you'll get it figured out and using a variable resistor will surely give you some insight into the issue. Good luck!
You are very very very smart teacher in the world woow because you simply the deficult
Thank you very much, I appreciate it!
I'm getting 5 volts on one of the wires, but then I take off the Sensor and run a paper clip to it, it's reading N/A on my scan tool. So does that mean I'm not getting ground? Maybe my ground wire is short? Because my cooling fans aren't turning on at all. I'm measuring 5 volts. And when I have it plugged in and engine turned on with a scan tool I'm reading around 1.5-3.2 volts. It drops down to 1.3 ish when the engine is hot. But still my fans won't turn on. I'm guessing it's the ecu ground?? I'm not even sure anymore! I'm confused. You didn't mention in the video about what would happen if the ground wire is short! Please help explain it to me. Thanks
Hi Scott! With the sensor disconnected, you would see 5V as you've mentioned. With the sensor disconnected, and with a jumper across the harness, (going back to the computer), the computer would see near 0V which would indicate a very hot condition. You're saying that your scanner says N/A which I would assume means Not Applicable. This isn't correct. See what your voltage says. With the sensor plugged in, you're seeing a voltage reading from 1.5-3.2V which sounds correct. And when the engine is hot, you read about 1.3V which again sounds correct. Are you getting a code for the ECT sensor? And if your coolant fans aren't coming on, then I would suspect that you have an issue with the coolant fan(s) circuitry.
great video.. done subscribe..my thermistor is broken.. can you tell me that thermistor detail?
Thanks for the subscription. You say my thermistor is broken and want to know that thermistor detail. You'll have to be more specific as in how is the thermistor broken; open, skewed, etc.
@@stuzman52 i use airflow 449 from mitsubishi but inside my thermistor is broken.. so i want to replace to the new one, but don't know the detail of the thermistor.
@@puts88channel24 Maybe just give the dealer a call and he can get the correct thermistor for you. Have a great day!
Ok I understand so if the engine is cool the iat sensor read high voltage so the the fuel ratio burn a little rich and when the engine is warm up the voltage drop and engine fuel ratio go down so the engine sound goes down ok and the map read the same air intake as well as the 02 sensor right
You are correct with the IAT as it will make small adjustments to the air/fuel ratio. The ECT will make larger adjustments to the air/fuel ratio. I believe the IAT is used mainly for measuring the temperature of the air coming into the engine to know the weight of the air. As for the MAP and O2, these two sensors measure the intake vacuum to determine the load on the engine, (again for air/fuel ratio) and the O2 sensors are used to determine the amount of oxygen in exhaust to again fine tune the air/fuel ratio.
Excellent tutorial Sir.If you may ill you plese do tutorial on ECU internal circuits and schematics.Thanks.
Thank you Leon for leaving a comment and for the suggestion!
Great teacher
Arthur Fricchione 😀😀 Thanks again Arthur!
Put upper intake manifold Gasket on it and now won't start but cranks fuel rail don't have pressure
Not sure what car you're talking about. If it's the Suzuki, check to make sure the ground wires are bolted underneath the intake manifold.
Another great video. Thank you.
I would appreciate if you could kindly explain the reason for the following hypothetical scenario. Say a fuse was continually burning out after being replaced. Say the circuit was for the left front headlamp. Say there was a short where a wire in the circuit became exposed and was rubbing against the metal body of the car. My question is this: What could be an explanation why the short would cause the fuse to burn out? Thank you
Thank you toyo for the comment on the video. With all circuits, there must be a load. Think of the load as what's doing the work and of course with all loads, there is resistance or the property which impedes the flow of electrons. Let's use conventional current flow for this example, although we know that electrons actually travel from the negative side of the battery to the positive side.
Electrons leave the positive post, goes through a fuse, switches, relays, etc. and finally out to the load. These electrons will travel through the filament, (there's our load and resistance) and then make their return trip back to the negative side of the battery. As you may know, the negative side of the battery is connected to the engine block, chassis and to the sheet metal of the car. Think of all these things as the negative side of the battery. So, when electrons leave the negative side of the battery, goes to the metal chassis where the B+ shorted wire is, we bypassed the load which means very low resistance to the flow of electrons. And that's when the fuse blows. Another way to think of this is to imagine that we took a wire and jumped directly across the battery posts. This will create the maximum current flow out of the battery since we don't have any resistance, (load) to impede those electrons. The reason we have fuses in circuits is to protect the wiring. And each wire size is rated for a safe maximum number of amps. Hope that helps you out toyo.
Great video.
Hey stutzman question . The two wires going to my iat has 5v across it . But the scanner is seeing 0volts on the display and -198 degrees . This is anew pcm and a new iat sensor , neither the older new iat show a resistance value when I check them directly. I checked continuity of both wires going to and back from pcm to iat . Both check good . I am at a loss . Same thing with old pcm it’s a 1994 dodge Dakota 3.9 mpfi if that matters. If you can steer me correct I would appreciate it . Thanks again
Are all AIT sensors negative temperature coefficient or can they be positive as well?
Blinded By The Light on cars you will find all of the sensors to be NTC. You’ll find PTC sensors in the industrial field.
Thanks, the reason I asked was because when I tested the sensor on my 2007 doge Caliber, the resistance went up as the temperature increased.
Blinded By The Light That’s very interesting as I’ve never ran across one like that. That’s probably how it works, and you could check with your service literature to be sure,
great info thanks
Thank you hddm3. I know it was a little long, but I wanted to cover everything possible so that guys can troubleshoot these systems.
Can I get your opinion on some live data i'm seeing ( if you have time!)
With obdii scanner looking at live data for voltage and temp of ect ( degree celcius down here used).
I get good data as engine warms up, gets to 60 degC and voltage jumps from 1v up to 4.23v.
It does this everytime, so I assume its the second resistor or similar turning on.
Now it gets weird:
The engine temp live data continues to be accurate and changes as it should ( fans kick in at 80deg),
but the voltage graph on live data shows constant 4.23v no change over time. At the same time I"m looking at voltage across ect using voltmeter and it shows voltage is changing not constant.
So computer knows what is correct engine temp, but its voltage output on live data stays at 4.23v ( until engine
goes under 60degC and it jumps back to just one resistor.
I swap ecu......same thing. any thoughts on that one?
I'm assuming that this is normal operation for your vehicle especially since you changed the ECU and it's doing the same thing. If you have the service literature, it may even mention the operation of the sensor which I suspect that it's switching in the second resistor inside the ECU. If you don't have any issues with the car and it doesn't give a code for the ECT, I wouldn't worry about it.
@@stuzman52 thanks for reply, it is good to know the car is reading correct temp, even though on the obdii live data the voltage for temp is not coreect on second resistor.
I'm sure it will lead to solution eventually but for now car is fine as is.
appreciate your video very helpful indeed
Well done great video hope you make more or Dease video. Can you make a video of alternators regulated bij the pcm
+Autocrew Stadskanaal I'll keep it in mind for the future. Thanks for commenting!
That 5V reference seems to be used in all kind of sensor circuits. One thing I've noticed this past decade when my battery is failing (on many different vehicles now) is a sag in idle speed. My theory is that at slow idle my alternator is unable to keep base voltage up, and that translates into a sag in the 5V reference baseline. That sag seems to allow idle to drop, without the usual automatic correction from the PCM. With a little gas and some time for the alternator to recharge a failing battery, all is well. I haven't come across a better explanation -- any thoughts?
Hey Dave. You always give me these thought provoking questions (smiling)... Your theory sounds good, but there is one flaw that doesn't make sense. I can't say for sure what the part number is for the voltage regulator inside the PCM, but all regulators that I've run into needs at least a couple of volts above it's output voltage for the output voltage to stay stable. I looked up the data sheet for the 7805 regulator and it can maintain a +5VDC output where the input voltage can vary from 7V-35V. So, even when the battery is failing, the 5V should still be constant. I can't explain that when the battery is failing, why does the idle speed drop, unless there are other things going on such as bad connections at the battery or some other place. I could see that if the generator was failing such as having a bad diode that AC voltage could get on the DC bus line. And with that scenario, all kind of things would be possible and not just with the idle speed. I'll have to think about it some more Dave. Good question though, and thanks for dropping in and taking the time to comment and for watching the video.
If your reference deviates away from whatever that voltage should be then you've got a problem. Reference voltage is supposed to be the one stable constant for all of your sensors.
My problem with your theory is that the alternator should be putting out about 12-14v minimum right? Using a resistor it drops to reference voltage (4.5-5.0 most cases). So it shouldn't negatively affect the reference circuit in anyway unless system voltage drops to below 5 volts. Your car isn't going to stay running with such low system voltage anyway so in that regard the problem would obviously be the alternator. Reference voltage is usually provided by a pin from the ECU. You can probe the reference circuit directly at the ECU and look for deviations there. Reference voltage shouldn't have anything to do with the alternator unless it's an obviously malfunctioning alternator (which should be obvious due to poor battery+ voltage)... both for total voltage and stability of that voltage.
I was surprised the first time this happened, after a parking lot boost 10 years ago. I couldn't maintain idle without goosing the throttle. But after a few minutes of driving, no problem. An alternator needs to be spinning at a minimum rate to generate power, which is why I'm thinking that voltage is sagging at such low (~300/min) RPM. Of course when this happens in a parking lot you don't have the arms or tools to do diagnostics. I just know the problem resolves after a few minutes of recharging with engine on.... This has happened with three different vehicles now, it's becoming a recognizable pattern. Any ideas?
spelunkerd For my vehicle anything under 500 RPM and it will begin to stall. How are you not stalling under 300 RPM? That's my cars starter speed. High lift cams? Sounds like a bad alternator to be honest. Are you using some kind of inverter on these vehicles. There has to be a common denominator. Something electrical you are introducing into the 3 cars that is drawing electricity. Parasitic drain perhaps? Nothing should mess with that 5v reference because it comes from inside the ECU itself. The resistor is inside the ECU then pins out to specific wires. Also the reference voltage has a ground circuit that it might monitor going into the ECU too. 1 or multiple pins for reference voltage out and reference ground in.
Can you make more of these theory based video,s please.
keith farrell Hi Keith. I'm a little busy with a lot of other things, but do see some more electrical related items coming up in the near future. So, stay tuned.
thank a lot, subscribed yessss
You're quite welcomed and thanks for the sub...
I have ect volt high code p0118, been trying to solve the puzzle for a couple of weeks now,
this is one damn excellent video on understanding ect ( or iac etc), much appreciate your posting it.
I'll keep working on my problem till I solve it, this info will be extremely helpful.
One thing I dont understand is why there is an internal earth? I assume its different to the chasis or battery
earths though connected in some way. Just by way of example lets say you use chasis earth instead of
internal earth for example in video, what would be the outcome?
Glad to hear you're finding the video helpful. The internal ground inside the PCM is to reference the 5VDC for the reference voltage which is used for the ECT or IAT circuits. It's possible that you can connect the external battery ground, but more than likely it's isolated. The reason is that the battery ground will have a lot of voltage spikes on it from all of the accessories on the car such as coils, motors, solenoids, etc. When checking the ECT or IAT circuit, it's best to use the internal ground for these circuits as the signal will be cleaner especially if you're using a scope to look at the signal over a period of time. You could try referencing the battery ground for these circuits with your voltmeter to see if you will get a voltage as some systems may have the external ground connected to the internal ground.
Good luck on finding your issue!
@@stuzman52 thanks so much for informative reply, car is ford falcon au ( 1999), very common car here in australia, amazingly reliable cars but getting a bit old now.
thanks
What would the PCM see if IAT is unplugged? Thanks for the video!
Roberto Santiago Rodriguez You would most likely get a P0113 code.
stuzman
Yes, of course, thanks so much!
I was referring to the computer reading a voltage equivalent to cold temperature and enriching the mixture as a result hence vehicle would run properly when cold and verify there was something wrong with the IAT. Am thinking of this also a way to test the IAT if no voltmeter was available and vehicle only ran rough when cold. Just a thought. TX again!
Roberto Santiago Rodriguez Zig If you unplug the connector the computer would see 5VDC which the computer would interpret as-40F/C. While the connector is pulled off, you could place a jumper across the two terminals. The computer would see this has 0 VDC. The computer would see this as a very hot condition. These two tests are used for circuit operation and wiring integrity. You could monitor the PID to see how the computer responds.
I did it, I disconnected the IAT sensor on my 1995 F150, 5.0 liters 2wd, automatic and the truck drove definitely better while cold. Of course, the PCM was smart enough to know it wasnt -40 degrees Fahrenheit outside so it turned on the Check Engine Light. It must have been using a low temperature parameter because the subsequent enrichment of the mixture to compensate for cold air, caused the engine to no longer run lean and got rid of the hesitation and lack of power. Temperature outside was actually 78 degrees Fahrenheit; hope it helps someone. Thanks again Stutzman for your explanation.
Glad to hear that the explanation helped you out Roberto and good to hear that your vehicle is running better!