On a 1996 GMC Jimmy. For the past 3 months, I regularly (once every 2 weeks?) get a engine warning light resulting in code 440.
Initially, I was advised maybe it's just a bad batch of fuel or tightness of fuel cap. Obviously after so many repeats, this is not the problem.
So I don't get hosed going to a mechanic right off the bat, what would be the causes of this issue and the methods of diagnoses and possible repairs or replacements required?
I don't notice any coincidingissues with the vehicle and fuel economy has not dropped since the start of the problem (although in the past month, since weather is colder, fuel economy has dropped noticeably!) Thank you.