SL/R230: Supercharged SL500 Intermittent P20D4 Load Limit
Thread Starter
Junior Member
Joined: Oct 2011
Posts: 27
Likes: 1
2006 Chrysler Crossfire w/M113 & 6sp
Supercharged SL500 Intermittent P20D4 Load Limit
I just bought a 2006 SL500 that has a RENNtech supercharger installed on it. Most of the time the car runs great, however it has an issue on part throttle around 2000 RPM. When going part throttle, maybe 20% to 30%, the car will sometimes buck/cut power. I have not seen the issue in low throttle or WOT situations. It does not do this buck/power cut every time, its intermittent. It seems to happen around 2000 to 3000 RPM, at least I have not seen it happen outside that range. I have pulled codes and it throws a P20D4 "The load limit is active (P1999)" code when this happens. The seller said it doesn't happen when in manual mode, and so far I have also not seen it happen in manual mode. It happens more often when going up a hill, which makes sense with the code I am getting. It seems like I am hitting some load limit in the tune and the ECU cuts the throttle. I attached the freeze frame data I just pulled tonight.
Anyone have any experience similar to this? Were you able to fix it?
Anyone have any experience similar to this? Were you able to fix it?
Joined: Nov 2016
Posts: 7,847
Likes: 3,496
From: Maryland
2015 SL400 (M276 Turbo), 2014 C350 Sport (M276 NA), 2004 SL500 (M113), 2004 Audi TT225 (BEA)
Call RENNtech and tell them what you just posted here. It does sound like a torque-limiting function.
Joined: Nov 2016
Posts: 7,847
Likes: 3,496
From: Maryland
2015 SL400 (M276 Turbo), 2014 C350 Sport (M276 NA), 2004 SL500 (M113), 2004 Audi TT225 (BEA)
Something is whacky with the datastream numbers.
- Engine coolant temp is kind cold to be testing. It should be closer to 190°F.
- Inlet manifold pressure being 938 psi is implausible.
- Fuel tank cap Open. Really?
- Fuel tank level 61 gal. Really?
Joined: Nov 2016
Posts: 7,847
Likes: 3,496
From: Maryland
2015 SL400 (M276 Turbo), 2014 C350 Sport (M276 NA), 2004 SL500 (M113), 2004 Audi TT225 (BEA)
If you do a Google search, you will find a lot of info. For Mercedes, it sounds like P20DA can be a bad MAF.
I'm curious, though. When I had my 2004 SL500, I wanted to add a supercharger but could not find a manufacturer that still made them. Can you post a pic of your engine?
I'm curious, though. When I had my 2004 SL500, I wanted to add a supercharger but could not find a manufacturer that still made them. Can you post a pic of your engine?
Thread Starter
Junior Member
Joined: Oct 2011
Posts: 27
Likes: 1
2006 Chrysler Crossfire w/M113 & 6sp
RENNtech was the first ones I emailed when I got the car. They offered to sell me their tune for this kit, but I am a little hesitant to go that route. They confirmed that the kit was not installed by them when I gave them my VIN, so right now I don't know who tuned the car originally. It must be tuned though because it runs great besides when it hits that cut.
I agree about the numbers, they seem off. Coolant definitely was over 88 F, my guess is that is in C even though the scanner says F. For the others you mentioned, yes those all seem odd to me as well. Even the time since engine start is not correct. I drove at least 15 minutes, then sat idling another 10 to 15 before driving another 5 or so before I hit the cut. I am using an Autel MK808 with the correct Mercedes car selected. I also have a STAR DAS but right now the laptop doesn't want to power on, I am trying to fix that.
Yeah I did see that in my googling, but the fact that it happens in the same conditions leads me to believe it is not a bad part. If it was the MAF I would expect it to act up at all RPM. I have a couple spare MAFs from my M113 crossfire, I might try swapping to a known good one just to see.
One more thing I did notice last night was that I have an easier time reproducing the problem when going up steep hills compared to flat ground. That pushes me more towards a load limit in the tune.
I am going to see if I can data log some pulls today to compare when it doesn't hit the issue to when it does.
I agree about the numbers, they seem off. Coolant definitely was over 88 F, my guess is that is in C even though the scanner says F. For the others you mentioned, yes those all seem odd to me as well. Even the time since engine start is not correct. I drove at least 15 minutes, then sat idling another 10 to 15 before driving another 5 or so before I hit the cut. I am using an Autel MK808 with the correct Mercedes car selected. I also have a STAR DAS but right now the laptop doesn't want to power on, I am trying to fix that.
Yeah I did see that in my googling, but the fact that it happens in the same conditions leads me to believe it is not a bad part. If it was the MAF I would expect it to act up at all RPM. I have a couple spare MAFs from my M113 crossfire, I might try swapping to a known good one just to see.
One more thing I did notice last night was that I have an easier time reproducing the problem when going up steep hills compared to flat ground. That pushes me more towards a load limit in the tune.
I am going to see if I can data log some pulls today to compare when it doesn't hit the issue to when it does.
Thread Starter
Junior Member
Joined: Oct 2011
Posts: 27
Likes: 1
2006 Chrysler Crossfire w/M113 & 6sp
If you do a Google search, you will find a lot of info. For Mercedes, it sounds like P20DA can be a bad MAF.
I'm curious, though. When I had my 2004 SL500, I wanted to add a supercharger but could not find a manufacturer that still made them. Can you post a pic of your engine?
I'm curious, though. When I had my 2004 SL500, I wanted to add a supercharger but could not find a manufacturer that still made them. Can you post a pic of your engine?
Joined: Nov 2016
Posts: 7,847
Likes: 3,496
From: Maryland
2015 SL400 (M276 Turbo), 2014 C350 Sport (M276 NA), 2004 SL500 (M113), 2004 Audi TT225 (BEA)
I would have loved to have supercharged my SL500. Kleeman was the other company that made a SC kit for the SL500. When asked why they stopped making the kit, I never got an answer. Seems to me that means they were problematic. BTW, nice, clean engine bay! (Over 20 years ago, in my VW days, I had installed a Neuspeed SC on my Jetta with the 2.0 liter engine, so I have a little experience with aftermarket bolt-ons like that.)
Going uphill puts a load on the engine and requests more boost. Not sure how the RENNtech SC is controlled, but I bet they rely on the MAF or use a MAP. Somehow the ECU is detecting too much load for the tranny and is cutting power.
I would get your MB Star working again (maybe a new (used) laptop). I also have the Autel MaxiDAS MK808, but use it less and less. I really use only XENTRY/DAS or LAUNCH Creader Elite 2.0 BENZ for my Mercedes and save the Autel for my kids' cars (Honda, Lexus, Toyota). That said, the Autel should work, but those numbers don't lie with regard to reliability or accuracy of the tool.
If RENNtech does not have the VIN in their records, it is unclear what tune, if any, you have. That could be a major problem or cause of what you are experiencing. How long did the previous owner have the SC on the car? Is that why they sold it? Not sure what RENNtech wants for the tune, but that may be the best way to go. I would at least check any fuel trims for rich or lean conditions. The previous owner may have just put bigger injectors in, thinking that would be sufficient for fueling. Maybe the previous owner can fill you in a little better on the history and other facts about the SC, etc.
Going uphill puts a load on the engine and requests more boost. Not sure how the RENNtech SC is controlled, but I bet they rely on the MAF or use a MAP. Somehow the ECU is detecting too much load for the tranny and is cutting power.
I would get your MB Star working again (maybe a new (used) laptop). I also have the Autel MaxiDAS MK808, but use it less and less. I really use only XENTRY/DAS or LAUNCH Creader Elite 2.0 BENZ for my Mercedes and save the Autel for my kids' cars (Honda, Lexus, Toyota). That said, the Autel should work, but those numbers don't lie with regard to reliability or accuracy of the tool.
If RENNtech does not have the VIN in their records, it is unclear what tune, if any, you have. That could be a major problem or cause of what you are experiencing. How long did the previous owner have the SC on the car? Is that why they sold it? Not sure what RENNtech wants for the tune, but that may be the best way to go. I would at least check any fuel trims for rich or lean conditions. The previous owner may have just put bigger injectors in, thinking that would be sufficient for fueling. Maybe the previous owner can fill you in a little better on the history and other facts about the SC, etc.
Trending Topics
Thread Starter
Junior Member
Joined: Oct 2011
Posts: 27
Likes: 1
2006 Chrysler Crossfire w/M113 & 6sp
Thanks! Yes most of the car is well done. There is some questionable work done to the interior though, lots of stuff glued back together. Seems someone didn't know how to properly disassemble the center console and just glued it back together. That will be getting fixed later.
It does use the MAF, and it seems like the ECU is running the NA software. I am talking with Josh from the Mercedes Swap Shop and sent him some info on the software version and he confirmed that. I am leaning towards having him convert an ECU to run 55K software to switch over to using MAP instead of MAF. He is the one who swapped my Crossfire so I trust him. I am not sure what RENNtech wants for the tune either, they haven't answered that yet, but I feel the car must have some tune on it already. I don't think it would run properly if it wasn't, but maybe I am wrong. I am worried I will still have the issue with their tune and be back to the same point just with a lighter wallet.
The previous owner bought the car already supercharged, around 2013, so he had it 10 to 11 years. He said it had the issue the whole time and he just lived with it. It is using the stock M113K injectors which is what originally came with the RENNtech kit. He put about 40k miles on the car.
It does use the MAF, and it seems like the ECU is running the NA software. I am talking with Josh from the Mercedes Swap Shop and sent him some info on the software version and he confirmed that. I am leaning towards having him convert an ECU to run 55K software to switch over to using MAP instead of MAF. He is the one who swapped my Crossfire so I trust him. I am not sure what RENNtech wants for the tune either, they haven't answered that yet, but I feel the car must have some tune on it already. I don't think it would run properly if it wasn't, but maybe I am wrong. I am worried I will still have the issue with their tune and be back to the same point just with a lighter wallet.
The previous owner bought the car already supercharged, around 2013, so he had it 10 to 11 years. He said it had the issue the whole time and he just lived with it. It is using the stock M113K injectors which is what originally came with the RENNtech kit. He put about 40k miles on the car.
MB World Stories
The Best of Mercedes & AMG
Manual Mercedes? 6 Times Sindelfingen Let Drivers Have All The Fun
Verdad Gallardo
Mercedes SLR McLaren 722 S Is Extremely Rare Example Modified by McLaren
Verdad Gallardo
8 Classic Boxy Mercedes Designs That Have Aged Like Fine Wine
Verdad Gallardo
Flawlessly Restored Mercedes 190E Evo II Heads to Auction
Verdad Gallardo
Electric Mercedes C-Class Unveiled: 11 Things You Need to Know
Verdad Gallardo
Mercedes EQS Gets A Major Update: Everything You Need to Know
Verdad Gallardo
5 Underrated Mercedes-Benz Models That Don't Get the Love They Deserve
Verdad Gallardo
Mercedes 300D Has Pushed Well Past 1 Million Miles and It Ain't Stopping
Verdad Gallardo
10 Most Reliable Mercedes-Benz Models You Can Buy Used
Verdad Gallardo
Joined: Nov 2016
Posts: 7,847
Likes: 3,496
From: Maryland
2015 SL400 (M276 Turbo), 2014 C350 Sport (M276 NA), 2004 SL500 (M113), 2004 Audi TT225 (BEA)
WOW! The last thing you want to do is run lean under boost! You know best if you have dealt with the same engine in the Crossfire, but I would want RENNtech to chime in since they developed the software originally. I have a feeling that it's going to be stupid expensive. Everyone seems to love RENNtech, but I have heard their customer service isn't the best.
All that said, it seems you need a proper tune and not someone futzing with injectors, etc. (been there and I've done that). You may want to also confirm that the SC pulley is original to the kit and not something smaller for more boost. I'd want to look at the LTFTs to see if fueling is OK.
EDIT: I can't believe the previous owner lived with the car like that for 10+ years and 40k miles. What fun is that?
All that said, it seems you need a proper tune and not someone futzing with injectors, etc. (been there and I've done that). You may want to also confirm that the SC pulley is original to the kit and not something smaller for more boost. I'd want to look at the LTFTs to see if fueling is OK.
EDIT: I can't believe the previous owner lived with the car like that for 10+ years and 40k miles. What fun is that?
Last edited by JettaRed; Feb 4, 2024 at 12:03 PM.
Thread Starter
Junior Member
Joined: Oct 2011
Posts: 27
Likes: 1
2006 Chrysler Crossfire w/M113 & 6sp
My Crossfire is NA still. I actually bought this car because I was going to pull the SC off it and swap it on the Crossfire. I have since decided not to do that, if I SC the Crossfire I will go with a factory M113K SC instead. I will say I am also not impressed with RENNtechs customer service, but to be fair they aren't the ones who did this install even if it is their kit.
Both short and long fuel trims look good to me. Staying between 5 %and -5% which seems pretty normal. Engine load seems high at idle to me, around 20 to 25% in park fully warmed up. Engine load seems pretty normal while driving though. Only other thing jumping out to me in the logs is the ECU never sees boost. I need to check where the MAP sensor is pulling from.
Both short and long fuel trims look good to me. Staying between 5 %and -5% which seems pretty normal. Engine load seems high at idle to me, around 20 to 25% in park fully warmed up. Engine load seems pretty normal while driving though. Only other thing jumping out to me in the logs is the ECU never sees boost. I need to check where the MAP sensor is pulling from.
Joined: Nov 2016
Posts: 7,847
Likes: 3,496
From: Maryland
2015 SL400 (M276 Turbo), 2014 C350 Sport (M276 NA), 2004 SL500 (M113), 2004 Audi TT225 (BEA)
The ECU probably will never see the boost because the car was not boosted to begin with. It should, however, measure ambient air intake pressure and vacuum to calculate load. Maybe that is where the problem lies. With a NA car, the ECU will only expect to see 0 relative psi or vacuum, not boost. I'm getting out of my depth here because I do not know what logic Mercedes uses and if there is an "on/off" setting to recognize boost pressure or not. This is why a conversation with RENNtech would be helpful. Seems to me they would be eager to help sell you some software.
(There was a post back in November of a guy in Florida that got his car tuned at the RENNtech facilities in Florida and during his return trip home (2-3 hours) he lost control when hydroplaning and totaled his car. Wanting to be able to transfer the tune to his replacement car, RENNtech wanted to charge the full amount again because it was a different car. While perfectly in their rights to do so, it seemed a little disloyal not to give a new customer some kind of break on the re-tune. I may be getting all of this wrong, but that's what I remember. https://mbworld.org/forums/sl-class-...-renntech.html)
(There was a post back in November of a guy in Florida that got his car tuned at the RENNtech facilities in Florida and during his return trip home (2-3 hours) he lost control when hydroplaning and totaled his car. Wanting to be able to transfer the tune to his replacement car, RENNtech wanted to charge the full amount again because it was a different car. While perfectly in their rights to do so, it seemed a little disloyal not to give a new customer some kind of break on the re-tune. I may be getting all of this wrong, but that's what I remember. https://mbworld.org/forums/sl-class-...-renntech.html)
Thread Starter
Junior Member
Joined: Oct 2011
Posts: 27
Likes: 1
2006 Chrysler Crossfire w/M113 & 6sp
Yes, I confirmed the MAP sensor is getting its reference directly behind the throttle body, before the SC. So what I am seeing the logs makes sense, vacuum to 0 PSI. I don't see any easy way to get a reference after the SC to verify how much boost its running.
Unfortunately my conversation with RENNtech was very one sided, they didn't really want to give me any info. I do understand from a business perspective why but unfortunately that isn't helpful for me. I don't have a price from them yet, but my main worry is I spend $1,200 (seems like their going rate for an NA tune, so I would guess it would be at least this much) only to still have the same issue.
Unfortunately my conversation with RENNtech was very one sided, they didn't really want to give me any info. I do understand from a business perspective why but unfortunately that isn't helpful for me. I don't have a price from them yet, but my main worry is I spend $1,200 (seems like their going rate for an NA tune, so I would guess it would be at least this much) only to still have the same issue.
Joined: Nov 2016
Posts: 7,847
Likes: 3,496
From: Maryland
2015 SL400 (M276 Turbo), 2014 C350 Sport (M276 NA), 2004 SL500 (M113), 2004 Audi TT225 (BEA)
That's really unfortunate. Baffling why they are not being helpful. The prices for some of their stuff reeks of arrogance, so maybe that attitude is pervasive. Are they a sponsor here? Not sure. Maybe referring to this forum might help.
Good luck finding the right tune. But I do think that is your problem.
Not really sure if @BenzNinja can help. I know he does some programming, but not sure about tuning programs.
Good luck finding the right tune. But I do think that is your problem.
Not really sure if @BenzNinja can help. I know he does some programming, but not sure about tuning programs.
Thread Starter
Junior Member
Joined: Oct 2011
Posts: 27
Likes: 1
2006 Chrysler Crossfire w/M113 & 6sp
I did, $2,250 for the tune 
. They did offer to check my ECU for free to verify if it has their tune or not though, I would just need to mail it to them. I haven't decided what I want to do with the car yet.
. They did offer to check my ECU for free to verify if it has their tune or not though, I would just need to mail it to them. I haven't decided what I want to do with the car yet.
Joined: Nov 2016
Posts: 7,847
Likes: 3,496
From: Maryland
2015 SL400 (M276 Turbo), 2014 C350 Sport (M276 NA), 2004 SL500 (M113), 2004 Audi TT225 (BEA)
Sounds like RENNtech=BOHICA, but I don't see where you have much choice if you want to enjoy the car. Thing is, trying to sell the car will be tough if anyone test drives it and knows anything about these cars. Not sure what you paid for it to begin with, but you do have a rarity in that car. I'm not sure you'll get 500hp safely, but it should be a nice boost when working properly.
