xtyper

Say I get an aftermarket tune and then go purchase a new spare ECU from the dealership to swap into the car for service visits. Then suppose 2 years from now I have a warranty issue and swap back the stock spare ECU to take it in for diagnosis. Is there any way for the dealer to determine that the spare ECU has only been used for that brief period of time after swapping? Put another way, does the ECU have some sort of logging mechanism that records its time and/or mileage spent in a car?

This is all hypothetically speaking, of course.

Even Money

I think it would be easier to find a dealer that is willing to work with you. Maybe it's just that way in SoCal, but my dealer here is easy to get along with. I'm willing to bet that if you have an issue, they are going to figure out what you're up to, especially if it's big $$$.

SonnyakaPig

Agree with the second part about MB likely being able to figure things out if the issue is big enough. But, regarding the first point about finding a dealer that is cool to work with, it really depends on what part of SoCal you live in.

My local service department is anything but cool.

Regarding OP's question, I wouldn't think alternating ECU's by itself would cause any warranty issues. It most likely comes down to the specific problem.

For example, if you melted a piston, the dealer would seriously want to know what you did to cause the severe engine damage. At that point, if they could tell that your ECU does have a mileage counter and it does not match the ECU for your car's odometer, they would likely dig.

If your power steering unit goes out, whether your ECU matches your odometer probably isn't going to matter that much and the dealer probably wouldn't care to look. (Assuming you haven't changed to a different pulley).

dodger63

I think, not sure someone else chime in but it tracks the milage.

dodger63

I think, not sure someone else chime in but it tracks the milage.

SonnyakaPig

Would be good to know. I imagine it does count the mileage.

A buddy of mine who owns a BMW was telling me that he heard that dealers can tell if your ECU is tuned by the size of the file. So, if your car is brought in for warranty work and you have a tuned file and your tuned file is a different file size, that it can be seen.

I've never heard of this before, but it at least seems plausible. My friend didn't know if this applys to MB's.

dodger63

All I know is I was going to order another (still em) and dealer wanted vin (obviously) and milage..

SonnyakaPig

That makes sense.

Even if you get an ECU from a non-dealer parts guy, you still have to get the ECU registered for your specific car.

I don't know if you must go to the dealer for this matching procedure or if non-MB-dealer repair shops have the equipment necessary to match your ECU to your VIN/car.

derspi

There's a good chance the immobilizer is tied into the ECU. I know this was the case with late-model hondas and acuras.

GHAZAN

No, I know it gets hooked up to Germany to get a VIN attached to it. They may even want to charged 1-2 hours of labor depending on the stealer. Not sure about mileage.

SonnyakaPig

Yes, I believe there is a charge.

CZ55

I was also curious about this. I found a wrecked C300 and I was about to but its ECU for 300 dollars not to tune my own ECU. But the company told me in order to use a secondary ECU they have open the original ECU to match the files. So the option of buying a spare ECU idea didn't make sense to me. I'm not sure about this but I think there is some kind of an algorithm between the ECU and the car and it sets some sort of codes every time you start your car.

dodger63

I think there just vin coded, were as it needs a special code vin/vehicle specific.

_AMG_

I would get the EZ Flash from OE Tuning. You can switch between your tune and stock tune on the fly.

dodger63

And there race fuel tune for that matter

SonnyakaPig

As many tunes as you want.

dodger63

Just remeber u can only use one at a time! Hahaha

_AMG_

+1

SonnyakaPig

LOL. True that.

justthebest

So, I bought a second ECU along similar thought lines - the parts guy that sold it to me (deals with tuned cars on a pretty regular basis) warned me that there was a slight chance that the new ECU would not match the current vehicle mileage & there would be significant problems. I never had the ***** / extra time in case it messed the car up to install the new ECU. Just food for thought.

dodger63

Mthis has 2 that seem to work perfect

MiamiAMG

I'm almost sure it logs your mileage

xtyper

Thank you guys for all the feedback, very helpful.

However, I have yet to see a definitive answer on the original question posed. I'm hoping that one of our acclaimed tuners chimes in here.

aleksandar1099

Just to throw in my 2 cents,

The tuned file must be EXACTLY the same size as the original file and have a correct checksumm performed on it or else the car will not start. Not only that, but I think people are over estimating the power of the star diagnostic system. It cannot track and identify the size of the file on the ECU.

In regards to the OP's question. You will need to purchase a new ECU from the dealer, and have it VIN coded. It helps to have someone you know at the dealer, or else it will be a very awkward conversation with the service advisor asking why you need another ECU programmed... To be honest, unless they have a reason to doubt you, you can roll into the dealer with a tune without any problems.

Hope this helps!

Thanks
Aleks

SonnyakaPig

Good feedback. Thanks.

Regarding where you can get a second ECU, you don't necessarily have to get them at a dealership. I could have purchased one at a discount -- compared to dealership prices -- from a MB mechanic. But, like you said, you will need to get it Vin coded at a dealership.

Regarding the tune's file size, what you said makes complete sense.