It would have been interesting to see a scope waveform on both the potentiometer and the EGR control. I suspect the reason the bidirectional controls weren’t working well was that it depends on the potentiometer to do the test. If you notice it failed in higher duty cycles but the new valve showed higher duty cycles were lower potentiometer voltage. Seems it being pegged made the bidirectional controls not want to work since it was saying “I’m already here”. That also supports the code saying it’s a closing performance. Idk how else it would tell other than potentiometer voltage. That’s obviously what you were alluding to in your wrap up but the data would be interesting to back it up. At the same time getting the car out of your garage is cool too lol Cool video as always. I had a recent slam dunk with a scope analysis on fuel injectors and using a pulse sensor to narrow down a misfire to cylinder 5. The car got all new fuel injectors anyway but it was cool to have data to back it up. The scope is my go to these days. I always try to use it.
In the video you raised a few questions about why the fuel trims behaved the way they did. I'll answer some of them here but the majority of them are covered in about 24 hours of training classes and this really does need to be covered completely, so this is only the "Cliff Notes" version. First, Oxygen sensors DO NOT sense oxygen. When we used to think that they did, because that is what the O.E's taught us, it led to situations that were very confusing to figure out. The proper name for them is a "Lambda Sensor" or "Lambdasonde". This Jeep is a speed density system. With the engine controller knowing the barometric pressure, the engine speed, the intake air temperature, and the absolute pressure in the intake manifold it can perform a very simple calculation and figure out how long to turn the injector on for and supply what should be the correct amount of fuel to the cylinder(s). In a perfect world, where the O2 concentration in the air is always the same, and the fuel pressure is correct, the injector flow rate is correct, and the fuel is correct etcetera the computer would always deliver the right amount of fuel. In the real world however, there are lots of things that fail to be what they are expected to be. In a speed density system, when you open the throttle, or allow any air into the intake manifold, that causes the absolute pressure in there to rise. As far as the computer is concerned, that rise in pressure means there is more air to charge the cylinder, so it needs to calculate a longer injector pulse to account for that additional air. The computer essentially sees that as an increased load on the engine. In this case there is extra "air" getting into the intake manifold from the EGR being stuck open. Seeing an increased load the computer as mentioned previously commands more fuel by calculating a longer base injector pulse-width. But instead of it being "air" it is actually inert gas because there is little to no oxygen in the EGR gasses. The result is an engine that is over fueled so there are a lot of combustibles in the exhaust and the sensor responds to that by generating with a high voltage and we see negative fuel trims as the response. BTW. Have you investigated Chryslers O2 "Goal Voltage" yet?
Another excellent diagnosis. I noticed that the bad EGR potentiometer signal response seemed to be the reverse of the replacement unit. I wonder if the ECU was initially adjusting LT fuel trims in the opposite direction (of expected) due to this incorrect signal.
Yes I noticed this too. I agree it makes sense the PCM is adjusting fuel delivery based on the based interpreted EGR position and therefore causing stoichiometric imbalance resulting in the fuel trim adjustment we saw.
Looking back that is what was wrong with my Ford 2.0 4cyl. Slightly rough idle and negative fuel trims (-10). I didn't know at the time to test if it was fully closed. It did change how it ran with the scan tool test. I'm sure now it wasn't closing all the way or at lest would have tested that. Good video.
I was diagnosing a very rough idle on an early 2000’s Honda Civic, no DTC, just wouldn't idle. Fuel trims were all over the place, took all day before I looked at the PID for the EGR lift, found it showing the valve was open. Removed the valve only to find it lodged open with rat turds,😆 No parts required, but several hours of time.
Ford is one of those manufacturers that our shop will not put an aftermarket alternator on any Ford that has the smart charging system in the car. Aftermarket’s just simply will not work with ford smart charging. We will also no longer put aftermarket cats on any car that is say within ten years old or less, aftermarket cats for any of these newer cars are just literally garbage anymore, you’re almost guaranteed a cat code if you don’t use an OE cat
It's always a pleasure to see you doing this stuff Matt, much apreciation from South Africa. By the way, I am still waiting patiently for that understanding of engine map or remapping video you promised to do one day. Cheers.
@@SchrodingersBox My bad Matt, maybe I was supposed to say PCM remapping, what is being changed during remapping, why people do it and what are the benefits if there are any. Thanks for the reply.
Ohhhhhhh. Yeah of course. That would be a good topic. Yeah I had to do that for my Trans Am when I did the supercharger - totally had to remap PCM including adapting it to speed density as I deleted the MAF sensor. Good idea. Will keep in mind!!!
@@SchrodingersBox Now you make me super excited here, I had no idea that you could take out the MAF as well, I am interested to know how does your PCM calculate stoichiometry in that case. I cannot wait for that video Matt.🙏🙏🙏
You should definitely re-watch my “secret of engine problem diagnosis: fuel trims” series as it’s probably the most important video on the channel for improving diagnostic skills. I am sure you have seen it by now but if not- definitely it’s the one series to watch on the whole channel!!
@@SchrodingersBox of course I've seen them, I was just impressed by the direct correction between stft and ltft, but as I said, every car reacts differently....as long as we live, we learn
I have kia Sportage 2018 diesel engine with almost the same egr and car has the same problem .. i will do your blowing method because it gives 💯 result ... i like people how think out of the box as you.
Outstanding tutorial from Part 1 to 2 👍 INTVITIVE,Schrodingers Box Take care,Schrodingers Box From Nick Ayivor from London England UK 🇬🇧 ⏰️ 3:34AM Good Night 😴 🥱 🌃 🌙
But then you run into the problem where, no doubt, OE's are going to be prohibited from selling directly in the future. Meaning you can only get it through a main dealer. And an EGR will cost an arm and a leg. I do wonder why the Aftermarket, given such a golden oppertunity, continues to work this way.
@Schrodingers Box I bought an Autel MS906PRO and an AESWAVE LineSpi smart B.O.B( the newer version with the battery voltage displayed on the BOB). Today I went to do my first scan on my new vehicle, a 2022 Chevy Traverse w 37,000 miles. No codes or anything but I have a question. I hooked the BOB up first, the the Scantool dongle to the BOB..and started vehicle. I auto ID the vehicle, scanned for codes...everything's fine. But on my BOB, the LEDs that identify the protocols being used light up and blink..as you know. My question is why would my 2022 Chevy Traverse 3.6 LT AWD have pin 7 on BOB light up( iso kwp (k) ), but nowhere on any schematics does it show that the DLC uses that pin, in fact it says not used? Any thoughts?
The code was for position, the fact that the volt meter didn't change was the clue. The voltage was between 4.5 and .05. on the new one. That should have been described in your book on how it works and you should have known that and that's what the computer was looking at, not fuel trims, if it was you would have gotten codes for that too. You could have hooked up a lab scope on the control wire and watched the PWM just to make sure the computer was working, after all that then take it off and blow thru it, there's your problem lady!
Matt. I super appreciate your analytical approach as always. Glad to see you uploaded this recently as I’m fighting a P0404 with my Honda accord. I noticed the desired position can be 0mm and the reported position can be 5mm. I highly suspect my 6 month old EGR valve is faulty. Unrelated note, is your trans am back together?
Thanks very much and yes funny you asked- I finally received the cylinder heads yesterday (after a 7 month backorder) and the trans am is back up and running today!!
Thanks for sharing, recently we checked few cars for smoke leak and found almost 90% of them had egr leak, Is this normal to have smoke coming out from egr (Electronic - 6 wires)?
That is because the EGR was always open so that’s how the PCM adjusted for this- by memorizing the LTfT setting to correct. What confused me is why the sTFT was countering it. That’s made no sense to me
Hello, this question is about the LTFT but I couldn't find the video to ask so I'm doing it here if I can? Thank you, LTFT - B1 [7.03% ] LTFT - B2 [5.47% ] I can't tell if it's adding of deducting? Thank you again
Thank you for your response, no issues, I just checked it and thought that it is possible that the injectors might be clogged, I could be wrong, I checked for vacuum leak and couldn't find one. Thank you again, your videos are very informative,
