I'm a new guy, so will probably get flamed until I figure everything out on the forum. This a general statement of my problems and cost to fix. 2010 Acadia AWD, 134K. Bought it with Service AWD light illuminated. Research suggested Differential Control Module was problem, easy fix. Wrong!!! took it to GMC dealer for full scan and found code P0017, 0073, and others. Dealer cleared obd and ran another scan. Same codes. Turns out I need timing Chains ($3500), and new catalytic converters ($1000). A bit of a shock but the car was so inexpensive and looked so good inside and out that I took a chance. Even considering the cost of repairs I'll come below KBB low retail value, I'll bite the bullet and go with the dealer fix for the warranty and experience. The whole point is : if possible take your car for a complete scan ($75 or $100) and KNOW what you're buying. I think you"ll save money in the long run. Flame on!!!