My Duramax has had a check engine light coming on intermittently for 6 months. It is the position sensor for the turbo. I had it replaced and also reprogrammed twice. It continued to come on within a day or two of being in the shop. They tell me now that they need to replace the turbo but that makes no sense to me. The light now stays on all the time. Truck runs perfectly and there is no performance problem at all or loss in mileage or any other symptom of a problem. It does it whether we are towing or just driving it unloaded. anyone else experience this or have any ideas?