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Further Re: Board computer

Paul Nicholson <paul@eisusa.com> wrote to Keith Arthur:

At 10:08 PM -0500 11/30/99, keith arthur wrote:
>Hi everyone.
>I just got my hands on my Mothers-soon to be mine- 1991 90.  I need help
>with the trip computer.  The average speed, time and miles to empty all
>work fine. but the instantanious fuel consumption, average fuel
>consumption both read 200. and the g->  always reads 0.0  what do i need
>to do get these working again.  If i reset the average fuel consumption
>it goes to 0.0 but as soon as i drive for any distance it goes 200.
>thanks in advance

It sounds like it's not getting information on the fuel consumption. My
guess, and it's only a guess, is that the ECU computes the fuel consumption
based on the injector commands, and somehow sends this to the trip computer.
Is the trip computer a separate system? If so, look for the communication
link between the two and verify the wiring.

Another possibility is that there is a break at the back of the instrument
cluster (IC).  Behind the fuel gauge is a potentiometer that is intended to
be adjusted via a small screwdriver inserted into the fuel gauge adjustment
shaft.  It calibrates the trip computer.  There is a process in the Bentley.
If a wire to this pot was broken, it might cause the same symptoms.  Also,
the trip computer mounts on the IC via a set of pins.  A bad contact could
be a cause.  There is a separate connector to the trip computer; it could be
badly connected.  If you are going to be a 90 owner, you will have to become
an IC repair expert sooner or later.

Kirby A. Smith   New Hampshire USA
1988 90q Titanium gray, 185 kmi
1988 90q Stone gray, 187 kmi 
1995 S6 Pearl effect, 84 kmi