Desired vs measured readings

2019 Hyundai gt n-line 1.6t gdi

Just curious about the difference between "desired" and actual values. I've been going through looking for discrepancies and found this one that doesn't match the desired numbers. Should the actual reading always match the desired numbers?

This seems to be Hyundai specific and I really can't find any info about this PID.

Backstory: the dealer techs are useless. No code misfires for 50k miles. My latest theory is a boost or exhaust leak

It's exactly what it says on the tin. Actual values is way up. Have you cheked wether the wastegate/blowoff is functioning? What does the sensor read with engine off?

Numbers should be close.

Compare to idle if the desired value is 800RPM 850 might be ok but not 1600.

Thanks for the reply! With engine off it's 980 and "desired" 134.The waste gate thinks it's working. I'm not sure what the values should be. Under normal driving it's 15.04% without moving. Under load or WOT it'll jump up to 50%. I also have high total fuel trims. Since it's warming up it's at about 10 most of the time. When it's cold it can be around 15-20. Lots of stinky sulfur smell when accelerating, also.

Seems like the sensor is giving erroneous readings. I'd start at measuring that and checking wether it has a desired valu that cen be measured out of circuit. If theres nothign wrong with it check the wiring and if possible maybe do a throttle body re learn if only for good measure. I used to work in a Huyndai dealership and I have some faint memory of a throttle body being changed out on a warranty or TSB type basis. Not a common fault though.

Thanks for your help! I have been avoiding getting in there myself for warranty reasons, but I don't think I've got a choice anymore. This has been an issue since day 1 and I've probably had it in no less than 30 times and they think it's fine although it runs like garbage. I'm helpless.

So you think it's the back pressure sensor giving bad readings and not the solenoid getting stuck? I'm not sure if I want to tangle with that myself

No back pressure when the engine is not turned on. Seems mor like an electrical fault. Depending on what type of sensor it is that is playing up there is definitely something wrong. Can you get the values in volts rather than hPa? Does the launch scanner do throttle body relearn? could possibly be related to evap or EGR too anything that has a moving part that relats to manifold pressure.

Check this link out

www.myo-p.com/Ford-EEC/EEC%20Help%20file...%20hardware/MAP.html

Thanks for that! I got the heat shield off so I could check things out. It's real tight back there. I couldn't find anything that could be the pressure sensor or hoses that lead to it.

I can get a reading in volts. It's at about 1.5v with the engine off and didn't change at all after startup. The voltage does go up under load. About 3v WOT.

I'm not sure if the TB relearns at all. I can clear the codes with my crappy scanner and that's about it.

One thing is after I clear codes or disconnect the battery, the car runs much better for a few days before returning to garbage.

The car usually pulls pretty nicely at wot above 3k. The desired and measured actually match up pretty well at that point

Maybe it's a software issue and it needs an update from the dealer? Probably goes back to the bad state after the drive cycle has been completed. To me it seems as if the system is working but for som reason it reads an erroneous value and since that error is present even when the engine is off it must come from either a high resistance connection or broken wire somewhere or it's a software error. I have seen electrical plug pins be mangled from factory on similar contacts so that is a strong candidate.

This video might help you find the sensor.

Hold up... You saying that it measurers exhaust back pressure with the map sensor on the intake? My boost readings seem to be accurate, or at the very least, the MAP reads proper atmospheric pressure when the car is off. It's actually easier to get to them the car in this video. I suppose the diaphragm could be damaged and giving the wrong reading while the car is running.
I just assumed there is a sensor somewhere on the exhaust that measurers back pressure like this one:

The boost is on the intake side not on the exhaust side. No throttle on the exhaust side. Unless your CAT is blocked.

Wouldnt put it past the chinese (Launch) to mistranslate the PID description though.

I'll mess around with it today. I can pull the harness and see if the readings do anything. Thanks for the info

Hope you get it to work. Check the intake air temperature sensor data too. if that one think it's 250F problems may arise. Should throw a code though

I believe the map also reads the temp. I'll check that out too. I would love nothing more than for a code to finally pop up. Would make my life so much easier

Unplug the MAP that should do it.

Unplugged the map and it didn't change the readings. I also think my crappy scanner might have something to do with it. May be doing the wrong calculations. The readings on the MAP show a similar pressure reading, 900hpa, on the MAP when the engine is off. Using torque pro, it shows the map reads proper atmospheric pressure. So I guess I have to assume that when my scanner reads 900hpa, that's atmospheric pressure in all sensors. This likely means whatever sensor reads the exhaust pressure is probably working as it should. I think the only solution is to toss a Molotov cocktail into the engine bay

Does the map read the same even if you unscrew it and it reads actual atmo? If it shows a steady value that could be a worry since it should fluctuate as the valves open and close.

Do you have any fligh recorder option on acy of your scan options?

Yeah. I did a deep dive into diagnosing the map a while ago. By all accounts, it appears to be working and registering proper values and temps. There are ways to log, but it's super complicated. Torque has a nice graph function in real time tho. It doesn't seem to pickup the PID for the "boost pressure upstream valve", so I can't use that to check it. Somewhere there is an update to that crappy chinese scanner I have, but it's nearly impossible to navigate the web of crummy websites you need to find it. I have been using the settings for a 2017 1.6t Elantra, which I didn't think would be very different, but apparently, they are or that thing just sucks. Either way, I will probably take it to an exhaust shop and have it checked out. Regardless of weather it's doing the proper calculations, it seems to not match the "desired" values.
If *900hpa* is atmospheric pressure, then maybe *1200hpa* by the scanner is a normal pressure while idling.
What doesn't seem to make sense is the "desired" value would actually be below atmospheric pressure. I'm not sure if that makes any sense

Wait no. The conversion app uncle Google supplies is wrong, actually. 900hpa is equal to 90kpa. So 980hpa is close to atmospheric pressure. It would seem the sensors are correct. I've got too much back pressure during normal operation and it evens out at full load. I'm not sure this indicates a clog in the exhaust

Yeah the anomaly is almost exactly 1 atmosphere of pressure so it looks like there is some calculation error. That upstream throttle sensor might be a dead end. Do you know wether the turbo is variable vane or fixed? The exhaust side sensor could be for the control of varible vanes and if those are gummed up with sut that might be the problem. I have seen it happen on VW buses with variable vane turbos they use a normal map sensor and a separate vacuum actuator on the turbo housing though and quite often crack the turbo/exhaust manifold housing aswell.