Chevrolet Repair: 2002 Silverado 2500 HD 4X4 6.0 FI, chevy silverado 2500hd, fi 2002

Question
2002 Chevy Silverado 2500HD 4X4 6.0 FI 135,000 miles. I am having difficulty trouble shooting my 4 wheel drive system. It has the 3 button electric shift on the dash. The other day the roads were bad and I placed it in 4H. It was fine for a few miles and then acted as if it was kicking in and out of 4 wheel drive. Now it will not engage at all. The lights on the push button panel light up as if it has shifted. While checking it out I pushed the 4LO button and drove down the road. It was in low range but I still did not have 4 wheel drive. I appreciate any opinions you have.
Thanks
Martin

Answer
It is probably the Transfer case actuator motor.  The motor and feedback circuit goes bad sometimes and the control unit has no idea where the motor position is.  To correctly diagnose this you will need a scan tool or wiring diagrams and good knowledge of a voltmeter.

Wayne