davepl

I want to be clear I agree with this 100%. You break it, you should pay for it.

That seems like a stretch to me (IF we're talking about non-current, previous tunes). Are you saying the microcontroller actually has a depth of 10 writes? Like 10X the required storage so it can go back through the last tunes and, in your words, "look at the tune itself"? I can't disprove it but everything I do know gives me serious doubts. I think there's a signature/hash history but not a full binary repository on the chip.

That said it's certainly possible, as GM could commission a chip that has that kind of redundant storage, but why would they when they can see whether the tune history is "approved" or not?

I guess one could argue that GM would have to prove that you modified the spark table to rule out a detonation-related warranty claim, for example. But I'd imagine just having an unauthorized tune at all would be enough to void your powertrain warranty. No?

bigsapper

I can see all attributes with my current tune right now using HP Tuners. GM Engineers have much more sophisticated tools at there disposal. Primarily because they don't have to reverse-engineer anything.

And I see what you're trying to compare. No. Chevy already knows what a stock tune looks like. They can pull that from "inventory" and compare with what they just pulled off your car. And yes, there is a flash counter that can't be overwritten. So if the count doesn't match what's on file, you have some 'splaining to do Lucy.

BRB...

bigsapper

Here's my current tune compared to my stock. I circled the highlighted area to show that the compare is showing the difference between the two.

BTW, it took me 5 times as long to screen snap, save and make this post than to pull up those two tunes to compare. check the timestamps on my two posts.

davepl

You're comparing a current tune to a disk file in HPTuners.... what does this prove exactly?

If your last two tunes are authorized, where does the GM dealer get a copy of the third last tune to look at for example?

bigsapper

At the end of the day, you may be able to fool a naive dealer or engineer a way around all the checks & balances. But to what purpose? If you're not trying to game the system, then this is more akin to asking "How many Angels can dance on the head of a pin?".

bigsapper

It proves that just because the CVNs match it's a trivial exercise to see that the tune isn't stock.

I don't suppose they can, but that doesn't mean they can't figure out that it's been flashed more than what they see in their system. It's more about the level of effort.

If you bring in a car with a rod hanging out of the block with a pristine E92 and no DTCs, how far do you think that's going to get you?

If you're in for warranty work because of a window leak, who the **** cares what you've done with your tune?

AORoads

Looks like LSX answered the question. Contrary to what I wrote before, I'd guess OP-Dave does not want to try it out with a new ECM-only and make a warranty claim re parts of powertrain somewhere in the future. That's understandable.

davepl

Actually I have no plans to modify the tune whatsoever, my car is completely stock, and because I bought the 10 year warranty (to quote Homer, "Extended Warranty? How can I go wrong!"), I don't plan to modify it.

I know the assumption here is that I'm trying to make powertrain or tune mods and get away it, but that's completely untrue. I'm of the opinion that the car's fast enough as it is, to be honest. At least for a convertible! And as said before, I think if you modify your car, including the tune, and break it, you should pay to fix it.

I do plan to experiment with some CAN and GMLAN stuff and don't want to brick my original ECM or BCM. This way I can drive it to and from if I go wrong somewhere.

The dealership is happy to assist and will set up a spare ECM for me. They do say it must be in the car, so I will take them my spare ECM and they'll install it in the car, set it up, flash it, and send me home with the original as a spare.

Oddly, I can get it from Rock Auto for half the price so even the parts guy said "If you can really get it for $165, buy it and bring it in!". Not even the dealership that I bought the car at, but it's where I go for all of our service. I hate being the guy who brings his own parts, but it's literally half the price...

Of course there's still one unknown. What if I install my spare ECM, over the course of time maybe they do a couple of module updates, and then 2 years from now I put back in my original ECM, which is then out of sync with the other updates - I assume that can cause a problem. Hopefully I don't hit that.

On RockAuto the ECM is $165, the BCM is $75, but I can't find the instrument cluster...

The three parts LSX mentioned are those I referred to in my "Minimal test bench" thread... we'll see if that's the canonical set or not! And we'll see if they can sit there as a test-bench connected only by networking and power and still chat with each other!

C5-JIM

The mileage IS STORED IN THE SPEEDOMETER.