We failed inspection because the computer would not give emission readings. on 2000 Ford Expedition

we replaced the gas cap and did a driving test to re-set computer and failed inspection again. how much will it cost to repair/replace computer so we can get emission readings?

by in Trenton, NJ on May 15, 2013
2 answers
ANSWER by on May 15, 2013
What are the trouble codes?
ANSWER by on May 15, 2013
what monitors are failing?