Gm auto track transfer case question

[THEFERMANATOR]

Pretty sure the late model auto trac system uses only the encoder motor at the transfer case. Early ststems also had an actuator on the front axle, but I thought around 02 or so they did away with it for full time capable systems. The most common failures on that system are the switch. The encoders fail every so often, but not a common failure part by any means. The encoder motor at the transfer case consists of a high torque motor assembly, and an encoder switch that relays the position of the motor shaft to the tccm(transfer case control module). It has a 2 hi, 4 hi, and 4 low position as well as when in 4 high, it is also used to engage the clutch pack for the full time operation(it is an on demand system that is electronically controlled to engage the front axle unlike most other systems that used a viscous bias differential). If it has the front axle disconnect, it is a very simple setup. It has a screw motor that runs out a piston when engaged, that piston puts pressure on a spring that in turn connects it to the actual plunger that engages the disconnect. And there is also a switch inside of it to send a signal back to the tccm to tell it when the piston is extended. If the correct tccm was put back in it, then the system is really good about siagnosing itself and knowing what is and isn't engaging. The speed sensors on the transfer case provide good feedback to tell the tccm if the shafts are actually engaging or not. With that many parts being thrown at the problem, I would be very concerned if the correct parts got put back in. The np-246 and np-263 actuatorslook VERY similiar to each other, but do not interchange. And the tccm's are all the same size and I believe areeven the same part numbers, but the programming is different depending on which style it is. Buying a replacement from a junkyard, they will sell you either style tccm, it isup to you totake it to a dealer for programming.

So you're saying auto 4x4 works, but not 4hi or 4lo, BUT the lights for them change?