I took my truck in for a p0191 code and dealer came back and told me that I had a chip (which I don't) and that is why it threw the code. I look on my bill which was $39. 50 for a half hour of labor and it said "customer states check engine lamp on with a code" then it says no codes showing no problem found. When I got back into my truck I rolled the key three times and the code was still there. He told me that they aren't seeing anything on their "big computer" and that the key roll method doesn't really mean anything. So i paid $39. 50 for them to do nothing. Sorry for the rant. Dealers are such crap.