Can anyone suggest a likely cause for the sudden under-reporting by 50%
of available range remaining on a full tank of gas with my '04 Accord
EX V6 w/ nav system's trip computer? I have reset the "history"
function both on filling the tank as well as repeatedly every 10 miles
thereafter while on the highway cruising at 32+ displayed average, not
instant, mpg, yet rather than showing a range of ~540 miles (17 gal x
32 avg. mpg) as it used to until 2 weeks ago, the trip computer display
has under the same circumstances taken to showing a range left on a
full tank of only 226 miles, effectively ignoring half of the fuel in
the tank at the reported avg. 32 mpg that is being achieved
consistently on the highway.

The range very slowly climbs to 250 miles as the tank reaches displayed
1/2 full, so the problem effectively goes away at a half-tankful but
then returns to under-reporting as further fuel is consumed, on the
order of a 50 mile deficit, compared to calculations of the amount of
fuel remaining based on the displayed avg. mpg for the trip, times the
same avg. mpg value.

Could this be a fuel float / sender problem in the tank, or is it more
likely the nav. system chip(s)? As the car is now out of warranty, I
don't want to spend more than $50 getting this fixed if at all
possible. Suggestions, anyone?