Anyone know where fault codes are stored on the ECU? The actual hardware location?

[lookaught]

I suspect it is stored on the EEPROM chip where the soft coding and Immobilizer code is stored, but can anyone confirm this? I suspect this may be the source of my check sum error code.

Thanks for any input!

[F16HTON]

Immob is not stored on EPROM IIRC, neither is the checksum errror, faults code are however. APR can remove the checksum error for you.

[lookaught]

The Immo is definitely on the EEPROM chip in the back center of the board.

Im not looking to have the check sum written out, I want to know why it's there. Do you know for sure that the check sum errors are not stored on that chip???

[MikeWire]

A check sum error is a software programming error. Why it's there could be a number of reasons - nobody will be able to tell you why it's there, just that an error occurred within the memory/software itself. Was your ECU exposed to anything like a power spike or drain, short circuit, or any kind of external element (rain, water, dirt etc.)?

The only way to get it fixed is to reflash your ECU. Although I suppose you could replace it, but then you would need to get it adapted to your car, Which would probably cost more than having flash with APR or some other software.

Maybe a dealership would be able to reflash it with the stock programming? Are you thinking of swapping eeprom chips?

[lookaught]

Ok here is the full story:

I originally bought a hard coded GIAC stage 1 ecu from Shawn in 2007. AFter $200 and two trips to the dealer to reprogram the immobilizer to this new ecu, my stock ecu no longer worked (different immo code).

Fast forward to 2009. Now that I'm going BT with a GTRS I need new software. The GIAC ecu uses a piggyback chip and not a flash, so in order to get REVO software onto this GIAC ecu I would have to pay $125 to have the chip removed, if it even can be removed. There are two other options:

1) pay to have the original ECU re-adapted to the car (and get raped by dealer costs)
2) have the ECU code cloned off of the EEPROM chip using an EEPROM reader writer. This involves sending both ECU's to a person who has the skill and equipemnt to do this, and this is the option I chose.

So I got the two ECU's back from the cloner and both now work in the car with all three keys. The problem, is that both now have a check sum error. I originally thought that this was a byproduct of the cloning process but after reviewing my codes that I pulled from last fall for another random CEL I realize that the check sum error was not new for the GIAC ecu, it was actually there since at least August (though not there in April 2008). Interestingly this check sum error will not actually trigger my CEL, which is how Ive driven around with it for at least seven months without realizing the problem (I didnt know what the error was in 2008 when I first skimmed over it in the list of CELs).

So when I put the stock ECU back into my car it has this check sum error, and the car has also coincidentally thrown a new CEL for a thermostat warning of some sort that is intermittent... this is what is making the CEL appear in my dash (I think). I suspect that the check sum error that was present with the GIAC has somehow been copied onto my stock ECU via teh cloning process, and that perhaps there is no check sum error at all on the stock ecu... the car had simply not been started/stopped enough times to clear it before I removed the stock ECU to send it back out to be re-cloned last week.

So the question is: where is the check sum error stored, if it is stored at all and not generated in real time every time the ignition is on. My plan of action is to put the stock ECU back in the car (check sum error and all) and have it reflashed with REVO software for the GTRS. Hopefully before then the check sum will disappear but if not, perhaps the flash will get rid of it. I also will inquire with the dealer for the approximate cost to reflash the chip with stock software, but if they want an hour or more of labor Im going to skip that step.

So that's the logic, and that's the reason for the question. And no, I don't plan to swap EEPROM chips, merely to clone the data. Finally, there is the chance that both ECU's simply had the check sum error and I never noticed in 2007 before the stock ECU was removed.

Moral of this story: Don't bother getting a chipped ECU, it is a huge fucking headache and has delayed my GTRS build for quite some time.