You have a slight problem.
First off, yes the car is OBD1.  But that should not be a problem for the
dealership.  EVERY V-12 made by Jaguar that had OBD  had OBD1 until the 1996
model year.  They should be able to handle it.  Go to a local parts chain
like Advance Auto or Pep Boys or someone and see if they can get a proper
reading.  Any time the dealership says they "think" they know the problem it
means that they are going to start charging you $150 an hour to
indiscriminately replace things until they get it right.  They charged my
buddy $200 to run a check on his XJR battery and tell him one of the cells
was shorted

You need to re-set the computer.  Make sure you have your radio codes and
door lock codes and then disconnect the positive terminal on the battery for
1/2 hour.  Re-connect the battery and the code may have gone away.
Disconnecting the battery is the same as re-booting your home computer.

I am not sure of the production numbers on the 1994 V-12 but I believe it is
much higher than than.  You can see them for sale on Ebay nearly every day.
In fact there are 2 of them for sale right now -- barely fetching $5,000.
IF there was potential value to these cars, collectors would be on them in a
minute and the price would be shooting up.  The rarest and most acclaimed of
the V-12s is the 1992 V-12  which will often fetch upwards to $35,000  --
$40,000.  It was an overlap car in the era of the square XJ40 -- it still
came packaged in the XJ6 Series III body.  For proper information on
production, simply contact the Jaguar Daimler Heritage Trust in Coventry.

Personally, I do not believe it will be an appreciating vehicle.  Whilst the
V-12 is a beautiful design and powerful plant, it also has it's drawbacks --
one of which you are experiencing at the dealership.  The 1988/1989 XJS
which came standard with the V-12 originally sold for nearly twice the XJ6.
Now they will barely sell for $2,000 - $2,500.  I have a friend who just
bought his in near perfect shape for $1800.

You should forget thinking about any potential windfall from your car and
simply enjoy it for the impressive, sleek, powerful beast it is.   If these
cars are selling for $5,000 in 2006 on Ebay  -- you will not live long
enough to see it appreciate substantially.  Just my humble opinion.

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