Dear Scotty,

love your channel, I have a 2004 Yukon XL made in Mexico, 331,000 miles, all original drivetrain (oil change, and lube every 3000 - 3500 miles) 5.3 flex V8 with automatic trans 4WD.  Typical repairs oil sending sensor, water pump, fuel pump, no biggies.  Changed the transfer case fluid on schedule 6 months ago and shortly after starting getting an intermittent “Service 4 wheel drive” message  every 500-800 miles. Then it started occasionally putting itself into auto 4WD on start up.  Had the codes checked but nothing showed for the 4WD.   Changed transfer case fluid again a week ago and now service alert showing up daily.  Don’t have a code reader but going to stop again at a parts store to get it read.  Wondering if it’s just the c-case sensor or the drive selection motor.  Hoping to “pull a Scotty” and get a half million out of the old girl.  Thanks - Doug