I have a 2003 Silverado 1500 5.3l 4x4. I’ve had the issue since getting the truck earlier this year. Sometimes after I start the truck, the 4x4 switch would say it’s in 4lo or auto 4wd even though the transfer case is in 2hi. I usually would put the truck in neutral and hit 2hi on the switch and I would hear the encoder motor shift around and then the switch would read correctly. After doing research, i saw a lot of people saying to replace the encoder motor. So I did so. After I changed it the truck was still doing the same thing. So I put the old encoder back in in hopes of being able to return the part (probably won’t be able to) or just sell it. But now after putting the old encoder back in, it won’t shift out of neutral. I turned the truck on and it said it was in 4lo like usual, I hit 2hi and I heard it only shift once. I usually hear it shift twice when it used to correctly shift. I have to keep on unplugging the battery to get the switch to reset because it will either keep blinking when I turn it off and back on or the switch will completely turn off and I can’t hit any of the buttons to try and shift it. Now after doing more research I’ve seen some stuff about a transfer case control module possibly being bad? I’ve tried looking up more but I wanted to make my own thread to see if anyone had some opinions on my situation. I have also cut open pretty much the entire wiring harness and haven’t found any broken or corroded wiring. Any opinions or help is appreciated as I’m getting irritated with this thing. Thanks in advance

 

I am not that familiar with all the electronics on the post 1999 Chevrolet's, but a bad TCCM is a good guess, as you stated. I have a 98 Chevy K-1500 with a manual shift 5 speed transmission and manual transfer case. Before that I owned an old AMC Jeep CJ-5, and the only thing "power" on that was the steering and the brakes. No A/C, no automatic locking hubs and the heater worked "okay" but those old Jeeps were tough as nails.

I wish I could put a solid axle with locking hubs on my K-1500, but way too expensive for my pocketbook. Back to your issue, have you run any diagnostic codes to see if the OBD II scanner shows any? That might be a good place to start, IMO.

 

the only code in the system is “encoder circuit” not exactly sure on the number of the code at the moment as I’m not at the shop.

 

I'm not sure what the encoder is, but if you have a push button 4 wheel drive where there's four buttons, starting from top down, you got your Auto 4wd then you 2HI, then 4HI then 4LO, you have an electric mechanical part called an (actuator) this is the part that moves you in and out of four-wheel drive, two-wheel drive Etc. my 02 Silverado was also stuck in 4Lo and that's the part I had to replace

 

Both of you gentlemen are correct. It is the same part that you both describe. It simply does automatically what an old four wheel drive transfer case shift lever did and does in a manual transfer case: it shifts between 4x2 and 4x4, and also shifts into high or low speed gear, all done without manually shifting the transfer case by hand.

This is the ACDelco part, sold on Amazon:

 

I’ve changed the encoder motor, transfer case control module, the 4x4 switch. Still won’t let me attempt to shift it. The switch will light up all the lights and everything every time I turn the truck on but after a couple seconds they all turn off. I have voltage at all wires that need voltage and I’ve checked for continuity on every wire on the system.

 

Let me also be more specific with the fact that I can shift the transfer case manually but it doesn’t fix the fact that the 4x4 system has me blocked out and it won’t let me attempt to shift the motor. Both old and new encoder motors are in the neutral position so if I were to rig it up to stay in 2 high, I still need to get one of the motors into 2 high. I’ve tried power probing the old motor but it’s shot. I don’t want to try doing it on the new one because I’m not trying to have to spend more money on another one

 

Got it. The only thing that comes to mind, is that your Transfer Case Control Module has gone south. This is the link to the part on Rock Auto, but I am sure that you can find one used, likely on eBay, if need be.

https://www.rockauto.com/en/catalog/...l+module,16844

 

its a long shot, but another possibility could be the transfer Case clutches are warn, typically that prevents being able to switch into 4x4 not the other way around, but you never know. Or a simple mistake I've made once was I was just low on gear oil preventing proper lubrication for the gear's to be able to move, but worse case scenario being bad clutches.. I got a whole clutch kit online for $100.