03 Silverado 1500 w NP8 transfer case and 5.3 L motor.
DTC code C0306 is set.
2WD/4WD shifting is disabled and 2WD light on switch panel is lit.
Using procedures in GM manual, encoder motor seems ok, but found
'short to voltage' condition on motor A control circuit. Also, motor
A and motor B control channels measure 108 ohm and 42k ohm to ground.
But, wiring harness seems not to have any physical faults (shorts,
etc.)

Much written about this transfer case in several GM vehicles and model
years, but nothing helpful. Info from NTSB/NHTSA suggests examining
some engine and chassis grounds. Hard to do, but all seems ok
although I have not checked ALL grounds yet.

Can the transfer case control module (>$300 for a new one from GM plus
programming) fail in such a way as to produce the test results above?
other possibilities?

"onekarguy" <onekarguy (AT) yahoo (DOT) com> wrote

In all probability it is the dash selector switch causing the issue, as this
is a very common issue on these years and yours are the exact symptoms that
usually are seen. Good news is it's a cheap fix and you can do it yourself
with no special tools and modest mechanical abilities. Pulling the dash is 2
minutes. The switch is about the same. Often the problem is cured by simply
resoldering the contacts on the back of the module, which is the cause of
the issue.

For what it is worth, mine was replaced by the dealer. That was under
warrantee and there is no telling if that was the actual problem. In the
first year I owned my truck I got a terrible misfire which they claimed was
ECM. Replaced and the misfire, though not as severe, never went
away until, by accident, I found the cause on my own some years later.

Just one of those things...

"Augustus" <no_one (AT) nowhere (DOT) net> wrote

onekarguy wrote:
My 2000 Silverado 5.3 4x4 LT had bad solder joints in the dash push
button switch assembly... Dealer replaced push button unit & all has
been fine for 7 years.

Must have been made on a Monday after tequila Sunday in
Mexico.

"Dennis Mayer" <Polaris1 (AT) execpc (DOT) com> wrote