Re: ECU Failing on 20v CQT??

[Robert Houk - WorkGroup Server Firmware <Robert.Houk@East.Sun.COM>]

   In message <3.0.3.16.19990407082208.21a7590e@n-jcenter.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
   "1111".

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!

					-RDH