Wondering if anyone has had the dealer give them issues or deny warranty repairs after you have tuned your ECU? If you have had no problems let me know too. I am getting ready to go in for mechanical not electrical issues but presume they will always check for codes etc and wanted to know if I should expect any problems.

Also, has anyone's dealer found out about the ECU tune without you telling them?

 

All dealers are different. Some are tuner friendly and other are not. My dealer basically told me is so many words that it would be a problem for them to warranty the car if it was tuned.

 

Are your mechanical issues related to the ECU tune? If not, you should not have any problem. Just make sure you tell them you don't want any software updates.

 

I have a mod friendly Service Director- told him no updates unless critical and then I wanted to know what they were first. But I believe in full disclosure so I did tell him about the tune before I even brought the car in. For the most part, they appreciate that and if they cant guarantee a flash wipe they will usually tell you.

 

To save yourself any future issues, spend the effort to talk to and get to know your service manager. Basically if any warranty issue is unrelated to the mods, they should fix it. Of course don't ever force a mod related warranty job on them. If both side are fair and open, it saves alot of headaches. My dealer went as far as swapping downpipes for me as a 'remove, inspect, and reinstall' job. Needless to say, I paid to play.

 

But will the dealer know if there was an ECU modification?

 

I can't comment on Mercedes but Audi, VW, Porsche, BMW all know if there is a tune if the car is plugged into their systems. The checksum on the ECU will or won't match and that's about it. Piggyback tunes are harder to spot since they don't affect the ECU.

Recently an aquaintence had to pay a signicant sum for an engine fault on an Audi RS6 because he was running a custom exhaust. There was no tune on the car at all. The law in the US is slightly different to the UK, the manufacturer has to prove the mod caused the fault.

 

Can you tune and then retune (preset to factory map) if you have a major warranty issue and need to take the car in?

 

You can on other makes of car, I assume the same is true on Mercedes. In theory the manufacturer still might be able to find out that a tune (or something) had been done because they might have logs where the car had out of spec data... or perhaps something was reset when the tune was removed that shouldn't be.

I tend to agree with ddtung - you have to think that you may have to pay to play. You may also have legal issues if you deliberately remove a modification to avoid paying for a problem caused by the modification. I don't know of anyone that has had problems of that nature though!

I have put tunes on cars in the past and, being honest, they've caused problems (clutch/coupling slippage, peaky performance, overheating) but nothing, thankfully, creating a major problem.

 

I will second that you need to have a talk with your service manager to let them know you are tuned and explain your issue. They should be able to tell you their stand on performing that warranty work. As long as the repair does not require an outside approval from a district MBUSA representative or a peak into the ECU, most dealers will be happy to perform the warranty work. They want to avoid getting into trouble and want to keep their customers happy especially if you bought the car from them.

 

MB clearly states that any mods especially to the ECU will void the factory warranty. The local dealer and the tech have the informal option to ignore your changes but most err on the side of the factory.

The other issue is that the dealer will add any new updates to your ECU every time your car comes in for service. I don't think these updates are incremental to the ECU but rather a complete ECU reload of the latest version for your car. That would mean your "custom enhanced" ECU changes would more than likely be overwritten in the process.

If you backed up your ECU before service, then when you "restored" your custom version you just may overwrite the latest dealer installed factory update in the process with the older version.

"Pay to Play" is the order of the day.

Be sure and remember to consider the future trade in and sale components. An expensive car with warranty issues isn't going to be worth as much as a factory stock one.

Either way it's your car and your decision.

 

every mfg will always say you cant tamper with their ecu. But unless they are diagnosing something in the tuning program they wouldnt see anything . If they were in that and showed some discrepancy in the programing I think the system would just attempt to rewrite or replace the program. If it did then you have lost your ecu program. If you have a program from renntech or evomsit, they are recorded by the mfg and will resend to you. If you have some generic or small company ecu program they may or may not keep it for you. Thats something you need to find out before you buy it. if you take your car in for some recall or other service it may or may not require the ecu to be reprogrammed , they may wipe it out without you even knowing it. you need to always be able to recopy your ecu so find all that out before you buy one
I think the thing to do is buy your ecu from a mb dealer. Alot of them sell renntech.

 

This has been discussed in hundreds of threads. Magnuson-Moss here in US requires that manufacturers must show causation of failure to be directly related to modification, if they choose to deny repair.

There are several canbus locations that record information outside of ECU, so reflashing or getting second ECU is useless.

That being said, AMG is now producing engines with identical power outputs of tunes and that will IMO make it difficult for Benz to deny claims based on simple power increases. But that doesn't mean they won't try....

 

MB clearly states it to cover their behind but the law is also there to protect you so that the manufacturer does not deny a failure in the radio unit because you have a tune.

As others have stated, if you are tuned, advise the dealer not to perform any ECU updates.

Do you want to be fighting a warranty denial with MBUSA? Hell No and that is the reason why you need to get acquainted with your local service manager.

 

I cannot speak for every manufacturer but I can 99.99% assure you that for Audi, Porsche and BMW at least they simply plug in to the diagnostics which is normally done every time you go in for a service and the system flags the car if it has had the ECU modified. The system automatically compares the data on the ECU with the default data. If it isn't the same it has been tampered with. There is no need to analyse what the tune actually does. These days I would suspect that the local dealer doesn't even get involved, the system calls back to Germany and reports the discrepancy. As a case in point my C63 coupe was held up in the workshop a few months ago because the dealer lost internet connectivity to Germany. As I and others mentioned before you are reasonably well protected in the US but this is not the case in the EU/UK.

 

Stay unplugged

 

Stateside, at least, only Audi has the automatic search process for mods in play. And thats for turbo based cars as my 2017 Audi R8 does not fall into that check protocol. I only tell my Service Director about my tunes on the Benzes and Porsches to avoid the "wiping" which would require a reflash.

 

Interesting. My information comes from service managers and senior workshop engineers, I've assumed them to be reliable. In the UK a lot of people who mod their cars get them serviced outside the dealer network and remove the tune if they get problems.

I recently got my RS6 checked for a tune because there were a few signs that made me suspicious and I got it with 3k on the clock. The service manager told me that the car had been into a service centre a couple of months back. It didn't get a TD1 flag then, I asked if it would have been checked and he said that it had gone in for an electrical fault so it would have been checked automatically. I was still concerned so I took it in, they plugged it in and said it was all ok thankfully. He also told me that they get a fair number of cars in that get TD1 flagged, I got the impression they don't mention this to the owner.

 

Im not sure what happens down under but I have had the same Benz Service Director for almost 12 years and have brought 8 AMG's to him over the duration, all of which have/had tunes, and he told me there is no auto search and report for variances. Now that doesnt mean the system doesnt pull the data but one has to be looking for it. This is the MBUSA dealer network that I have experience with so things could definitely vary outside of NA.

Porsche is the same out here; I have multiple Cobb tunes running on my last run of cars and no problems or auto detect.

Yes I think thats the same over here with Audi, they just take your car in and check it and tell you about it later when its already been TD1'd. I was even told that if you avoid hooking up the Audi then AUDIUSA will question the service call (I had asked one dealer for no updates).

Edit: I just got off the phone with my AMG tech and all he said was "They are crazy in Australia when it comes to checking on mods" LOL

 

There are nearly 30 Mercedes dealers in the US who are authorized RennTech dealers, each of whom will assure you that you are not going to have warranty issues solely as result of a tune that they installed. That is safe, albeit expensive route. Agree with Vic55--with any tune or mod its about knowing your SA and having an understanding of what the rules of engagement are before you play game. I come from the dark side of the W204 C63 world where a significant number of our cars are tuned. I would have to search, but I don't recall any instances where a warranty was voided solely as a result of the installation of a tune. There has to be a direct connection between the modification and the problem.

 

Any idea if you have a tune, can the dealer easily reprogram the ECU back to stock if I wanted them to? Thank you.

 

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Just in case anyone missed this the first time -


Thank-You
D.B.


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If they perform any kind of software update, it erases the tune.

 

If the engine blows I wonder if a dealer will try to determine if there has been a tune. Or maybe MBZ instructing the dealer to look for one.

 

So, a piggyback tune can't be detected if you remove before an inspection. To the car and any of its programmed parameters, it will be operating within spec. The piggyback just adjusts that information going back to the ECU to change what the normal operating parameters actually mean to the parts affected (turbo boost etc). An ECU Tune remaps those parameters and can easily be detected by the mfg because the car won't be operating in spec if they are testing parameters - let's say you have a failed turbo - boost was increased - you won't be covered.

With an HHT ECU tune like RENNtech, you can keep the stock mapping and remap in a handheld and swap from one to the other for service. With BMW, they have a counter in the ECU programming that can determine if a car has been remapped and then swapped back to stock etc. And, if the car is found to be modified BMW is notorious for logging that in the system and effectively making it VERY difficult to go through warranty claim issues. As I understand it, Mercedes doesn't have this counter.

All this said, owners in the US are protected by the Magnusson Moss Warranty Act. It does a number of things, including protecting the consumer from having forced service intervals at the dealership to keep your warranty in place (yes, they used to do that). In addition, it puts the 'proof' of a warranty claim denial at the feet of the manufacturer if they intend to blame a modification or non-OEM part as the reason for the failure. For example, if you have a head gasket leak, but you have an aftermarket exhaust, they can't deny your warranty claim because of the exhaust. They would have to prove that the exhaust caused the failure. That said, while we are protected, there is nothing better than the relationship and understanding you have with the service manager's position on these things - right or wrong they can make it really painful or a breeze for you and any issue you face.

Know your rights, but as with most things, it will come down to your reputation and relationships.