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Re: ECU Failing on 20v CQT??
In message <email@example.com> Mike Arman writes:
> If the ECU is reluctant to save the settings, this sounds very much to me
> like a failing EPROM - this sometimes happens with EPROMS in computer
> BIOS'es - replacing the chip solves the problem (although most of the time
> it is the CMOS battery that's bad).
If the EPROM fails, the ECU is toast. It's possible for a minor storage
error to occur, but this will always produce the infamous error code
Follow-up: for "practical" purposes, "EPROM"s are read-only memory,
"computers" cannot write/store/save information into them. "EEPROM"s
however are [typically] used by embedded computers for saving non-
volatile information (e.g., "error logs", et al) when such information
needs to be guaranteed across power-fails... Typically, embedded
computers (such as Audi ECUs) will [did] use ROMs (cheap in quantity)
for the actual computer program, not EPROMs. Hackers replace the ROMs
with EPROMs since EPROMs can be re-written indefinitely [typical life
cycles are currently in 100K write/progamming cycles range] with the
right "lab" equipment. Many "modern" embedded computers are using
"FLASHRAM" rather than ROM/EPROM, which are in-place update'able by
the computer itself (but in general a computer will not use its
"writeable" FLASHRAM for storage of "error logs", etc).
It keeps its "settings" - so far as these exist - in RAM. Things like
the current ignition timing for each cylinder, etc. In early ECUs,
this RAM is volatile - in the later ones it's not. Perhaps our
wrench friend was trying to dump codes after the ignition had been
switched off - assuming the memory was permanent when it's actually
volatile on this car.
I suspect this car has an intermittent or borderline problem that is
beyond the wrench's competence. In such cases, a damn good read of
Scott's web site always prepares you for the next conversation you
have with the guy. Very, very few understand how important the
electronics is - in a very real sense, post-1987 Audis are computers
with engines wrapped around them.
Current Audis are computer *networks* with cars infused/wrapped around
the various network nodes!