Problem Dave is you're smarter than you're suppose to be ...................They don't have mechanics that actually fix chit these days . If they can't plug it in and get a code ..............No Fault found Sir!
This is exactly why I left mechanicing at High Country Chev a few years back. There is no 'fixing' anymore. If the computer dont tell them whats wrong they are clueless. And if the customer start pressuring them then they just start replacing parts hoping that the porblem disappears. Its a conmplete joke in them shops now.