Need help tuning out P0238

[Stew]

I am getting a P0238 occasionally and not sure how to resolve it without altering manifold pressure. It's a little tricky nailing down the conditions triggering it since it doesn't happen very often and I can't drive around with my laptop logging all the time but the conditions where it's occurring seems consistent with the second quote below.

It seems like it's happening when psi is around 23 at around 3000 RPM. That is the max my boost peaks at and it will only get that high 3000 RPM and up. I am hoping there is a solution that does not involve reducing boost, I am pretty happy with my tune except for this little fly in the ointment. My tune is not the same as the one in the tune thread that is stickied, FYI.

Also, you can indeed disable the CEL for this code but that does not prevent you from going into limp mode, it still happens just no CEL.

Searching the forum only pulls up the following two posts with no solutions:

Well, I have an update. I'm having trouble with a pesky DTC (P0238) where I'm apparently getting a sensor voltage high problem.

Looks like I've got a pretty good reason for the over-voltage:

And

Had code P0238. According to what someone on facebook posted:

ECU saw a boost spike higher than it liked as sent you into limp mode...

P0238 Description
Turbocharger Boost Circuit High Input Conditions

Cause
Engine speed less than 3506 rpm, then the PCM detected that the Turbocharger Boost Pressure input was more than or equal to 4 80v (202 kPa), condition met for 2 seconds

Anybody comment on this for us laymen?

Thanks guys and gals!

 

[BNRacing]

Post your tune or email it to me jerry@badnewsracing.net and I'll take a look and see if I see any reason for it.

 

[Stew]

Wow, thank you! I stepped away from my computer for a few hours but I can email it to you soon.

 

[BNRacing]

replied to your email

 

[ScarabEpic22]

IDK but offhand I'd look at altering/upping the max boost allowed (not verbatim) in the tune.

 

[BNRacing]

It's gotta be the base duty cycle, its cranked way up where it doesn't need to be.

 

[BNRacing]

You should only ever need to raise the base duty cycle a few % here and there, nothing major. I see a lot of HPT tunes from people having problems where the duty cycle is super high, in the 100s all over the place. You should only mess with the duty cycle stuff if the car isn't meeting the requested boost. You should be logging turbocharger desired boost pressure as well as turbocharger boost pressure. If actual boost is a few psi less than desired, then you add up to 5% to that that table in the area you think it needs it. That's it.

 

[ScarabEpic22]

You should only ever need to raise the base duty cycle a few % here and there, nothing major. I see a lot of HPT tunes from people having problems where the duty cycle is super high, in the 100s all over the place. You should only mess with the duty cycle stuff if the car isn't meeting the requested boost. You should be logging turbocharger desired boost pressure as well as turbocharger boost pressure. If actual boost is a few psi less than desired, then you add up to 5% to that that table in the area you think it needs it. That's it.

Great advice. No need to crank the volume up to 100 from 50 when 60 will do...just leads to issues!

Start small, like the 5% Jerry recommended. If it throws it again, up it another 5%.

 

[BNRacing]

We'll get him sorted out for sure. His tune is pretty dang close, just that duty cycle and a few other improvements that I see could be made


Sent from my iPhone using Tapatalk

 

[buickz]

UPDATE - Found the issue. Max boost table. Evidently the ECT numbers mean nothing. Maxed out the right 3 cells and had full control of the desired boost to my limit again. In case anyone runs into it.

I seem to be having the same issue and after creating alternate tunes and maxing out the values everyone suggests I still cannot get my desired boost above 217kpa so I have had to add to the Base DC to achieve the kpa I want to run. Not sure what I am missing. Stew, any tips?

Thanks!

 

[Stew]

Hey buickz, sorry I didn't see your post right away.

Yeah, the Max Boost Limit table where it looks like you can set boost limits depending on ECT threw me off for a long time too. Either that table doesn't work correctly or (more likely) it's not labeled correctly in HPT, it wouldn't be the first time from what I understand. That's why at first I was jacking up the Turbocharger Base DC table, I just could not figure out what the problem was.

Even so, I still get the P0238 if boost gets too close to 23 psi so I'm still wanting to resolve that little niggle.

 

[BNRacing]

There are several tables not labeled correctly in multiple softwares. I've figured them all out through trial and error. It's annoying. Increase your boost vs. knock max airmass table and it will make more

 

[buickz]

No Worries. After discovering that little label issue I have all the control I want but I still get it in higher gears when boost is ramping in, it overshoots a little, hits 22+ psi, triggering code. 100% pedal gives perfect boost results all the time. Heavy part throttle will trigger the code when boost exceeds my desired boost even a little bit. I can drive to avoid it but sometimes in traffic when it happens its annoying. I will post back when I find a solution.

 

[BNRacing]

How bad is it overboosting? If it's only a hair you can just go into engine diagnostics and relax the overboost criteria. If it's more than a little bit you need to adjust your boost tables some.

 

[Flyer]

Please explain the mis named tables and what they really do. Im havig a similar issue with a p0238.

 

[buickz]

Thank You for the responses!!

I am just playing with the boost and wastegate DC to get it right where I want it to be. It just overshoots a little. No need to remove safeguards. Any more than 22.5lbs of boost floats my valves at 6K rpms anyway and chaos in-sues.

As for the mislabeled table it was just the max boost table. The temperatures seems to mean nothing as I originally only was changing the right most cell, 145 degrees, but my boost desired was actually never rising to that value. Then I looked at the cell next to it and DUH theres my logged desired boost number! making the right 3 cells equal made sure my boost desired was what I wanted instead of having to add Wastegate DC to get the boost I wanted.

Hopefully it makes sense.

 

[Flyer]

Yup. Thanks.

 

[Big Turbo Sonic]

There are several tables not labeled correctly in multiple softwares. I've figured them all out through trial and error. It's annoying. Increase your boost vs. knock max airmass table and it will make more

I am just a little bit confused as to what the final solution was here. I am trying to raise boost on my turbo swapped sonic GT2056. I am using HPTuners and I am having the exact same problem. I cannot get the desired boost to raise past 212kpa.

I initially thought the Turbo DC table is what raised the boost but since reading this thread I have lowered Turbo DC and now I am trying to figure out how to raise desired boost. I tried raising driver demanded tables by a significant amount to see if that works and it didnt.

How do I get desired boost to raise?

 

[Big Turbo Sonic]

UPDATE - Found the issue. Max boost table. Evidently the ECT numbers mean nothing. Maxed out the right 3 cells and had full control of the desired boost to my limit again. In case anyone runs into it.

I seem to be having the same issue and after creating alternate tunes and maxing out the values everyone suggests I still cannot get my desired boost above 217kpa so I have had to add to the Base DC to achieve the kpa I want to run. Not sure what I am missing. Stew, any tips?

Thanks!

Just an update. I tried setting my right three cells to my desired boost and did not get anything. So I changed all of them to what I wanted and I then had control of desired boost.
After dialing Turbo DC back and pulling some timing I was able to do a pull. Still threw P0238.
Went into Engine Diagnostic, disabled AAP 1, 2, & 3 and no more P0238.
Thanks for this great thread.

 

[Steelmesh]

Thank You for the responses!!

I am just playing with the boost and wastegate DC to get it right where I want it to be. It just overshoots a little. No need to remove safeguards. Any more than 22.5lbs of boost floats my valves at 6K rpms anyway and chaos in-sues.

As for the mislabeled table it was just the max boost table. The temperatures seems to mean nothing as I originally only was changing the right most cell, 145 degrees, but my boost desired was actually never rising to that value. Then I looked at the cell next to it and DUH theres my logged desired boost number! making the right 3 cells equal made sure my boost desired was what I wanted instead of having to add Wastegate DC to get the boost I wanted.

Hopefully it makes sense.

If it is overshooting, have you considered adjusting the "I" Intergral in the PID for the boost controller? I am looking at the E78 ECU for the 1.4T Cruze, but imagine there must be PID control in the E69.