S54 intermittent idle issues with code P0506 AFTER doing CSL/MAP conversion

[BeardedRyno828]

Just curious if anyone has run into something like this...

Every now and then when coming to a stop, and only after about a 20min drive or so, the idle will hang a bit high (around 1000-1100 usually), and if I sit there long enough it will go into Limp mode with code P0506- Idle Air Control, System RPM Lower Than Expected. I have noticed that when the problem starts to happen and I blip the throttle, the high idle will rise higher and higher. I have also noticed that if the idle starts to hang high and I just put it back into gear and drive off, there are no codes and everything seems fine.

This all started after going to a CSL/MAP setup *with an HP-converted MSS54 DME*. Pre-conversion the car ran decent. I went with a Geoff Steel airbox, had my MSS54 DME converted, and Hassan at HTE remotely tuned it.

Things to note:
-All throttle sensors are new, Pedal was new in 2019
-IACV is new (actually took care of a slight idle surge)
-All throttle bodies are CLEAN and adjusted to spec per BMW.
-Original throttle actuator
-Adaptations reset

I have been meaning to do some logs to try to see if we can find anything but I just haven't had the time to do so since this is my rally car and I'm in the middle of a re-prep (we had a rough last rally). I had the thought of putting in my spare throttle actuator for shits-n-giggles but I have a strange feeling that this is all in the DME and more specifically something to do with the HP conversion (not the tuning)... I DO have another DME on hand (another HP-converted one) but I was unsure if I could just do a full DME Read and then transfer that to another DME or if there was more to it.

Thoughts?

[Slideways]

Stock tune/airbox or DME swap sounds like the best test for this since you already replaced the ICV and TPSs. EWS might need re-syncing unless it is disabled. If there is still a problem, you might want to check the ITB adjustments again. Someone said it was tricky to adjust them correctly.

[AWE46M3]

Who did your HP DME conversion?

[BeardedRyno828]

Stock tune/airbox or DME swap sounds like the best test for this since you already replaced the ICV and TPSs. EWS might need re-syncing unless it is disabled. If there is still a problem, you might want to check the ITB adjustments again. Someone said it was tricky to adjust them correctly.

No EWS as this is an S54 swapped E36 M3. I highly doubt it’s the throttle body adjustment as there were zero issues pre CSL swap/DME conversion.

Who did your HP DME conversion?

A local shop to me, Performance Euroworks. Had an absolute nightmare of a time with them and would never go back. I’m half tempted to chase down an actual HP DME to toss in.

[AWE46M3]

No EWS as this is an S54 swapped E36 M3. I highly doubt it’s the throttle body adjustment as there were zero issues pre CSL swap/DME conversion.



A local shop to me, Performance Euroworks. Had an absolute nightmare of a time with them and would never go back. I’m half tempted to chase down an actual HP DME to toss in.

Kassell Performance will lace you up. Pull that thing and send it out to them. It’s ~500 for non HP DME’s to get it converted properly and flashed with CSL boot loader. You can have HTE or whoever you prefer for the tune do the rest.

[BeardedRyno828]

Kassell Performance will lace you up. Pull that thing and send it out to them. It’s ~500 for non HP DME’s to get it converted properly and flashed with CSL boot loader. You can have HTE or whoever you prefer for the tune do the rest.

I actually have a Kassel Performance HP converted DME here at my disposal, I just don’t know if I can easily pull the HTE tune out of my current DME and install it in the other or if I need to get someone else involved.

[heinzboehmer]

I actually have a Kassel Performance HP converted DME here at my disposal, I just don’t know if I can easily pull the HTE tune out of my current DME and install it in the other or if I need to get someone else involved.

Depends on what bootloader is running on both DMEs. Easy to check with mssflasher. Leave car as is, click "Identify ECU", swap in other DME in, reclick "Identify ECU". If both hardware IDs are 32500, then you're good to pull the full binary out of your current DME and flash it onto the new one. If the hardware IDs don't match and you try that, you'll brick the new one.

I'd also open up the DME that you suspect is faulty when you have it out of the car. Check for obvious signs of damage (burnt component, burnt board, melted stuff, etc.) and make sure the EEPROMs used are the correct spec. This post has some info on that last bit: https://nam3forum.com/forums/forum/s...=2536#post2536

[BeardedRyno828]

Depends on what bootloader is running on both DMEs. Easy to check with mssflasher. Leave car as is, click "Identify ECU", swap in other DME in, reclick "Identify ECU". If both hardware IDs are 32500, then you're good to pull the full binary out of your current DME and flash it onto the new one. If the hardware IDs don't match and you try that, you'll brick the new one.

I'd also open up the DME that you suspect is faulty when you have it out of the car. Check for obvious signs of damage (burnt component, burnt board, melted stuff, etc.) and make sure the EEPROMs used are the correct spec. This post has some info on that last bit: https://nam3forum.com/forums/forum/s...=2536#post2536

Fingers crossed that I have the time to mess with it this weekend! It’s not the end of the world if I don’t get it resolved before our next rally but it sure would be nice. The car runs *amazing* outside of this issue and has yet to be a hindrance while racing. I just keep my pocket OBD2 scanner hooked up so I can check/clear on the fly if needed.

[BeardedRyno828]

I swapped out the DME’s and loaded up my Fullbinary into the Kassel one, starts and runs so I guess I need to get it ready for a proper road test now.

I did open up both DME’s to compare, seems like my DME is missing some stuff.

My DME is on the left, Kassel one on the right.

[BeardedRyno828]

My DME

[BeardedRyno828]

Kassel DME

[heinzboehmer]

Hmm, I don't see anything that's obviously wrong with the old DME. It is hard to tell with just pictures though.

However, I've never seen an MSS54/HP that has those two MOSFETs on the right populated like on the Kassel one. Maybe they know something we don't...

NZ_M3 does your genuine CSL DME have those MOSFETs too?

[BeardedRyno828]

Hmm, I don't see anything that's obviously wrong with the old DME. It is hard to tell with just pictures though.

However, I've never seen an MSS54/HP that has those two MOSFETs on the right populated like on the Kassel one. Maybe they know something we don't...

NZ_M3 does your genuine CSL DME have those MOSFETs too?

from the looks of it, mine is just missing the stuff for the CSL flap (which I don’t have). I was wondering if those other pieces (MOSFETs) on the right had something to do with SMG? I can’t see what the vin is on the Kassel DME so not sure what trans it was intended for. Mine is definitely for a 6-speed manual.

First test drive this morning (25 miles to work) absolutely ZERO hiccups. Fingers crossed it’s good on the way home!

[terra]

Hmm, I don't see anything that's obviously wrong with the old DME. It is hard to tell with just pictures though.

However, I've never seen an MSS54/HP that has those two MOSFETs on the right populated like on the Kassel one. Maybe they know something we don't...

NZ_M3 does your genuine CSL DME have those MOSFETs too?

Looks like that DME was originally an mss52. The extra igbts are for the 2 extra cylinders.

[heinzboehmer]

Looks like that DME was originally an mss52. The extra igbts are for the 2 extra cylinders.

Aaaah that makes total sense. Thanks for that

Also, thanks for clarifying that they're IGBTs not MOSFETs. Am away from my spare DMEs and couldn't make out the writing on them from the pictures I've taken, so I just guessed