I would disconnect the battery for 5 min. while this is being done take your gas cap and blow some compressed air through the vent hole and make sure when you tighten the cap 3 clicks after tight, hook up batt. & see if this works.
go and look up chiltons repair book and it will have a page on CODES and will describe how to check codes at home with a paper clip by jumping a couple of terminals on the plug in module. you will be able to count the flashes of your service light and look up what the problem is in the book.
hope this helps
Link Sr.
Threaded Mode