my car is a , 2020 mercedes e53 amg 4dr 3.0 m256 engine

ecu part number : A2569001200

Hey so , I am having this really annoying issue.
I had got a stage 2 ecu tune & a tuned cpc module from Weistec , on my factory ecu of course . A few days after , I had my mechanic do basic maintenance brakes rotors, coolant flush & oil change , and changed all six spark plugs, unfortunately due to a damaged engine wire harness from changing the spark plugs ,(common issue with m256 platform due to heat from turbo and engine) it caused a short which burnt/damaged the ecu , after getting a brand new engine wire harness installed & a used replacement ecu which I had gotten programmed to my car, (thankfully my ecu was still communicating). First ecu had gotten came off of a gle 53.unbeknownst to me even though both use same part number ecu they are programmed differently depending on the model.

Weistec said most likely that is the reason why, & that the short caused the tuned cpc module to have gotten damaged. So they made me buy a new cpc module which is far from cheap, 2000$! after the initial 4000$! is ridiculous. But even with the new cpc module they hooked it up and it still wasnt revving & it remained stuck at around 2000rpm . So they told me go get the ecu from a e53 instead of a different model, & it should work then , even if the ecu is stock it should be able to rev perfectly fine with the tuned cpc. Following their recommendation & advice I bought a ecu that came off a 2019 e53 , got it programmed again , & with the hopes of the tuned cpc module working now which again i paid $2000 for !!! to work, but still the same issue it just won’t rev/accelerate. Is there anybody that can please help me , I would highly appreciate it !

 

Lots of sunk cost here. I'm sorry about that.

after they replaced your wire harness, was everything driving appropriately? Or are multiple things happening at the same time? You are replacing the engine wire harness and your tuning these modules at the same time?

I would recommend taking a CPC module back to stock, and taking the ECU back to stock. Report back after you do this to make sure the car is driving appropriately.

I can't imagine what modules are affected with a short from the engine wire harness that damages the ECU and I can't imagine what other damage follows downstream beyond the CPC. It sounds like Weistec might be shooting in the dark here and not giving you the best advice, which is go back to stock and make sure the car runs fine and then reconsider tuning after the fact. Sounds like they got your money though they made sure of that.

 

Thanks for the reply PeterUbers, Yes they did make sure to get their moneys worth out of me , but yes everything is working perfectly fine with the brand new wire harness, The car is working perfectly fine with the ecu being stock as well as the factory cpc module connected. But once I connect disconnect the stock one and connect to the tuned cpc module it just wont let me accelerate and the rpm is stuck at pretty much 2000.

as far as any other damages beside the ecu from the short, I had to replace the voltage regulator as well, the one thats next to the cpc module in the passenger footwell.

But again I spent 4k on a ecu tune and a tuned cpc so I would like to take advantage of it instead of having to acceptance that I threw that money out the window for nothing.

 

And to be clear:

at least for a few days before you did maintenance work, the tuned ecu and tuned cpc were working fine?

 

yea it was working perfectly fine beforehand for a whole week & thats when I did preventative maintenance, trying to avoid any costly repairs. But ended up causing unintentional costly repairs due to the short caused by the damaged wiring harness as seen here,

 

way to go again, Mercedes.

 

Yea , hopefully somebody has the solution to this stupid problem im having 🙏🏽😭

 

And what does Weistec think now:

- you replaced the ecu
- you got a new cpc
- things work fine in stock form

can you just upload the tune file to the ecu and Keep the cpc stock - and in this scenario does the car run fine?

how are you certain that the car is running normally in stock format?

it seems to me that the ECU tuned and the cpc tuned are not communicating appropriately and therefore there's this limitation at 2000 RPMs. It's like the ECU is calling for more torque, but the cpc and TCU are not allowing it.

 

Yes the car did work fine with the tuned ecu and stock cpc, & sorry but last night i connected the tuned cpc again & actually car is in a limp mode stuck at 500rpm , I dont know why i thought it was 2000rpm, im not sure if that helps a little bit & weistec is closed currently until tommorow so I will see what they are talking about now that I did everything they told me to do , only strange thing again is they said the stock ecu is supposed to work fine with the tuned cpc which its not, strange.

 

It's their cpc tune - or the module they sold you for $2000

 

both in one, its a whole new cpc module that you hook up, which is tuned . cost for that was $2000

 

I just received a message back from weistec, maybe there is some guy that can fix this issue by going over the code of the ecu to see if there is something wrong , im not sure, I have reached out to the guy that programmed the used ecu to my car to see if he can do something, But I will leave their reply below:
"
Weistec (Weistec Engineering)

Feb 23, 2025, 1:35 PM PST

What ever was done during the replacement of the ECU has caused some kind of software or coding conflict. Likely because you are using used ECU’s rather than a new one from the dealer.

Prior to your wire harness and ECU being damaged, the cpc worked

Something caused damage to the wire harness which then damaged the ECU.

I don’t know what process the place you went to did to get a used ECU from a different car to work, but what ever they did made it so that the special boot loader we use on tuned cpc’s does not want to work with the replacement ECU

You brought the car in and it appeared that your upgraded cpc was damaged which was a reasonable guess given that the ECU was damaged.

We programmed a new cpc to the car and it did the same thing.

That is what tells us that what ever was done to your replacement ECU’s to get them programmed to your car is the cause of the cpc upgrade not working

It might be helpful if you get a detailed description from who ever you had replace the ECU on the exact process and tools that were used to get the ECU’s programmed to your car.

Another potential option is to take the car to the Mercedes dealer with the stock cpc installed and have them install a new ECU"

 

Wow, a new ecu at Benz will run you $3000-4000.

I do not know if a cloned ecu will not play well with tuned cpc, but I have 3 cloned ecu's for my m157 and do not have an issue with the tcu (I do not have a cpc module on my w212 e63, however), my ecu's came from various donor vehicles such as GL450, SL63, ML550... its used in many Benz v8 vehicles - identical hardware. As you know, it's just the code that is a bit different and it's VIN coded.

I think the "coder" at Weistec should be able to solve this for you with a little more code analysis but I truly don't know.

 

When the mechanic was replacing the spark plugs and the wire is shorted, and when the ecu was damaged, would that be covered under the mechanics insurance policy? Would he cover the cost of a new ECU since it was during his work that this all happened?

 

Yea ,unfortunately I cant force anybody to do anything they dont want to do, I won’t give up though Im going to try and go back over there tommorow or tuesday to see if they can have their coder do better analysis. But im going to assume that Im going to have to take matters into my own hands by finding someone that can go over it unfortunately. & I can ask if the mechanic has a insurance policy , not sure if its too late since i already paid for all repairs out of my pocket. & because he kept saying it wasnt intentional, It was my first experience with something like that happening as well so I wasn’t entirely sure how to proceed at the time.

 

All you can do is ask - nothin is intentional but fair is fair

 

Your stock ecu can be simply repaired. I had the same story on my CLS and it was quite easy to make it working.
It seems that pcb paths are secured from this kind of shorts.

 

I agree with Peter in that the mechanic should figure how out to make you whole from their repair mistake. When dealing with insurance like this and it is out of the original mechanics league, you can take it to Mercedes to have them fix you up with all new stock items and yes, it’s going to be a fortune, but it’s going to be fixed and ultimately that is what the mechanics insurance is for and whether or not insurance wants to pay for your upgrades is perhaps a different story but just like if they damaged a expensive aftermarket wheel, they are liable. It sucks to go through, but everybody should be fine owning up to the mistakes cause it happens. I had a camshaft get broken on my lx by a mechanic after they fixed a timing belt cam seal leak warranty (cause the leak reoccurred) six months later. It was during Covid and it was a mess and parts were nonexistent, but we got it done together (me finding an me finding a part on a shelf in Fla after a month of searching) and have a great relationship to this day. Good luck getting it all sorted.