I've had a 997S that had no battery in it for 6 months. All the data was still there when I got her back on the road...

 

Lol what makes you say that? Of course they have non-volatile memory. They store all sorts of data long term that doesn't get wiped when removing the battery for any amount of time.
Where do you suppose the VIN, the odometer info, etc is stored?

In fact having non-volatile memory is a requirement for the OBD-2 standard...it has to store certain emission faults in NV RAM.

 

This is not correct. However, I do think its easy for someone with the proper tool to do so. It's too easy to update/fix things like mileage when swapping things like odometers. If they can do it and update all the right modules to reflect this, then I wouldn't be surprised if the O/R can be done too if someone really wanted to.

 

A friend wrote with a bit of information:

• Certain info coded in or logged (VIN, odometer, etc—and one would assume over-revs, reflashes, etc) is not something that can be altered with regular (dealer level) diagnostic interfaces; should require mfr level (ECU or car maker) for obvious reasons; would love to hear if information suggests otherwise
• New ECU coded to an existing 991.2 might be a different matter; cost for new ECU v downside from over-rev report would be the question there. Next question is disclosure.

This is an interesting case, and I'd like to hear/see more.

 

From prior experience, each dealer has a "Manufacturer level representative" that will remote or go on site to do certain module pairing/fixing/updating. But I also know plenty of Indy shops that can code a new or different cluster so it matches the correct mileage and no tamper dot or any of the like is apparent. Over-rev reports aren't far off I would think, as Mileage tampering would be more serious, in my mind at least.

 

Lol. There's a big difference between clearing adaptive parameters with an interruption of power and clearing things like *mileage*, operating hours, over-revs, etc.

Even my lowly, ancient '89 928 has NV-memory in the instrument cluster for retaining mileage. It has no interface for rolling back mileage and a new cluster can only be set forward from 0 and only under very specific conditions. And only once.

The airbag ECU for 90+ has NV-memory so that you can't make a 'deployment' disappear.

In either case, yes, if you crack open the units (good phooking luck with the airbag ECU) you could probably R&R whatever component functions as the NV-memory. Good luck getting clean replacements for 40-year-old chips...

In general, with the right skills, equipment and funding you can do just about anything to electronics.

However, the current gen of ECUs in 991s (and there are about 10 IIRC) have multiple layers that have to be hacked though. The first is, of course, encryption. On the other end, AFAIK every single current-gen Porsche ECU has to be vin-coded with the PIWIS before it is anything other than a brick. And the PIWIS doesn't operate in that mode unless it is Internet-connected to the mother ship. (The first observation is from the WSM and direct experience with the dealer on a warranty repair, the second was conveyed to me by a Porsche dealer tech.)

So, yes, I have no doubt it is possible to remove the engine ECU and install an ECU that shows no over-revs. But, I'm gonna bet that unless you're a state-sponsored hacker it's going to be really, really hard. You could do an ECU swap with PIWIS, but I would bet that all the NV-stored data is transferred. Even if not, somewhere there's a DB that knows that VIN X has had N engine ECUs programmed. I doubt that that info is easy for even a dealer to get though.

In any case, Occam's Razor for the OPs issue says that the over-rev reports were from two different VINs.

 

There must be a way to replace a failed DME. I assume that process would require entering the current mileage. I bet that it also requires participation from the mother ship to "unbrick" the replacement DME. So if it IS the same car perhaps the DME was swapped? (Caveat: I have no idea what I'm talking about... just thinking out loud.)

 

When I did it, ECUs did not have non-volatile memory. Sorry if I'm out of date.

 

It can be hacked. Might be difficult but possible.

 

I don't know what everyone else here has said, but there is one way to "erase" over-revs, from what I've read: technically, you can still see that there was *something* done to the CPU of the car, but the over-revs get set to 0. Usually this is done if a new engine is placed in the car, but supposedly needs to involve someone at PCNA. However, you will see somewhere on the DME report that some line item, labelled something like "computer resets" reads 2, instead of 1.