2005 Chevrolet Silverado 1500.

Dash lights = service 4 wheel drive
GM tech = jk
question = service 4 wheel drive light comes on & push buttons won't shift into 4 wheel drive
Answer: Well, there are a actually a few things that can cause this.
A faulty 4wd selector switch. (The switch you press with the lights)
A bad control module. It is located in the dash behind the headlight
switch. A bad encoder motor. This is on the transfer case.
A scan of the 4wd module is needed to check for any fault codes.

2002  Silverado 25000 6.0L V8 Vortec.
Question = Where is the MAP sensor on a 6.0 Vortec V-8
Answer: It is located right on top of the intake
manifold, closer to the rear of the engine. It
will have a 3 wire connector on it. You will
have to remove the plastic cover that is over
the intake manifold to access it. Very easy to
locate and change if needed. Lubricate the
new sensor's rubber boot lightly with some
lithium grease or silicone to ease installation
and provide a good seal.
1999 Chevy Silverado 4x4 5.3 Vortec.
Repairs for this problem = installed new transfer case, need new encoder motor.
Question = I replaced the transfer case due to burnt out clutches. Found the encoder motor to be
seized. I replaced the encoder motor, and it tried to work and then burnt itself out, has internal
open on the A/B motor circuit. Diagnosed as needing a new ATC module and encoder motor. Will
not have parts in for a while. Wanting to know if truck will drive with encoder motor removed and
front drive shaft removed.
Answer: Yes, you can drive the truck with the encoder
motor off and/or the front driveshaft out of the vehicle.
One thing you may you want to try, is manually
shifting the transfer into two wheel drive by turning the
fork with pliers or comparable tool. This won't do any
damage and then you could even reinstall the drive
shaft just to be safe. Either way would be fine, just
keep an eye for fluid leaks or debris getting in the
sensitive areas of the transfer case.