They completed a smog check on my 2001 Ford F350 with a 7.3 Diesel motor. I took it to another smog shop and there pre tester machine turned the truck off and didn’t do the test. I replaced the two batteries as one was bad. I drove 40 miles took it back and it failed again. They told me to drive 80 more miles and come back. They thought there also might be a wiring or grounding problem. I googled the problem, it gave me a list of items to check. I cleaned the battery post really good and didn’t find any other problems with the items on the list google told me to check. Google then listed Rays as a place that could make any repairs necessary. I dropped off the truck and they assured me they could make the repairs if there was a problem with a quoted price for repairs if needed. They call me in a hour later and said there was not a problem and it pasted. They only charged me for the smog test, I’m glad I took it to Rays