Hello. My friend has a 2006 Buick rendezvous 3.5l automatic with 200,000 miles  I removed the battery to replace the water pump on the vehicle. The water pump was not leaking so I put the battery back inside the vehicle. the car has power when I put it in the on position however will not start or attempted to crank over and lose all power when I try to turn the car on. I also unplugged a wiring connector when I was attempting to replace the water pump. I plugged the wiring harnesses back in and I disconnected the power wire  that’s just to the right of the fuse box thats on the top left corner of the engine bay. I connected the power back to the fuse box. If I need to reprogram anything I can do so as I own a high level scan tool (Autel reprogramming) . I just need to know what to do. The vehicle started the day before I attempted to replace the water pump. Vehicle may have blown head gasket and bad transmission just want to get the vehicle started for her.