1999 silverado 1500 stuck in 4hi

My truck is stuck in 4hi when I turn the key on service 4wd light comes on. An when I push 2 hi it flashes. tccm clicks then I hear a humming/buzzing coming from the tc shift motor an stays in 4hi I can push 4 auto an It goes into that but no 2 hi or 4 low I have two 99s so part are easy to get so I swapped out the dash switch with a working one from my other one. No change . Swapped out tccm (transfer case control module) no change. I believe my actuator is working as it should I hear it just like my other working 99 4wd system so I thought it's gotta be a bad shift motor but after reading lots of post here I'm thinking a bad wire ? Any input welcomed have an appointment at the shop the 7th of July if I can fix it before then I'll save 200 bucks what colors are the problem wires that every one has ? An is there a way to get it into 2wd if i cant fix it myself ?Thanks

I haven't check my fluid yet
I haven't ran it for codes I tried but the checker didn't have stuff to get to transfer case data

The problem you have is most likely the encoder motor. this is the motor that is in the transfercase. what happens is over time the blue Trac II fluid turns a very dark color. this is then a damaged fluid. use of 4WD has nothing much to do with this fluid being damaged .. you can never use 4 WD and this fluid will get damaged.

so I find you did not check the fluid with your post ...why ?

how long has it been since this fluid was changed ? 40,000 mi is the recommended .

I just bought the truck less than 2 weeks ago so its been hard to get time to work on it an yes I first thought it was the encoder/shift motor since that's were the noise is coming from but after reading other post that sound like my 4wd symptoms I'm leaning towards bad wiring or loose connection somewhere there was another post with my same problem from 2011 but he never said what wire he replaced or have the wiring schematics I could up load a youtube video an u could see what my truck does instead of me explaining it I could share the link?

X2 on the encoder motor. Since you have one available and have replaced everything else, why not?

Also if you can't fix it run it in AUTO 4WD to get where you're going.

When I run in 4 auto it's still locked it full time I think I got a meter today goin to check all the plugs to make sure all are getting power to the tc

So I just checked for volts on the wire that goes to the tc encoder there are 4 wires one thick red, one thick black .One thick orange . One small brown wire running from the atc fuse to the plug down by the tc encoder then on the other end from the encoder the wires are 2 thick red an black an the brown an orange are small

Volts from fuse box wire down to the plug

Red .000
Black .000
Orange 11.980
Brown .037-9ish

Goin to check what wires are hot right after the act fuse will update does anyone know what voltage these wires should be getting?

I just bought the truck less than 2 weeks ago so its been hard to get time to work on it an yes I first thought it was the encoder/shift motor since that's were the noise is coming from but after reading other post that sound like my 4wd symptoms I'm leaning towards bad wiring or loose connection somewhere there was another post with my same problem from 2011 but he never said what wire he replaced or have the wiring schematics I could up load a youtube video an u could see what my truck does instead of me explaining it I could share the link?

IMO the purchasing of an old vehicle requires the replacing of all the drive train fluids of the proper GM current spec's.. along with the transmission filter..

you still have not stated if the fluid is even in the transfer case ..or what the fluid condition is !

the encoder has many wires to it ... the big fat wires are power to motor the small wires are the encoder position wires..PCM needs to know what position the encoder is at all times. bad fluid damages this stuff.

If you find black colored fluid or no fluid then you will need this transfer case replaced / rebuilt .

So what wires should be hot out of them 4 wires ? I can't seem to find a wire diagram for the transfer case any were online that tells me what wires have volts an grounds that don't?

I took the atc fuse out an was able to drive it today in 2wd if i put the fuse in it goes back to 4wd

For $27 all the info you need to trouble shoot your issue can be had at this site.

http://alldatadiy.com/buy/

So I rechecked my wires an redid my ground an I think my wires are good three wires grounded out an the orange wire is hot at 12.55 volts the red an black wire grounds at 12.55 an the brown was 11.67 so I think it is the encoder/ motor

An I recheck my fluid cuz sumthing got me thinking it's supposed to be a special fluid that's blue in color right ? Well the fluid that's in the tc is red like fresh tranny fluid

So I rechecked my wires an redid my ground an I think my wires are good three wires grounded out an the orange wire is hot at 12.55 volts the red an black wire grounds at 12.55 an the brown was 11.67 so I think it is the encoder/ motor

An I recheck my fluid cuz sumthing got me thinking it's supposed to be a special fluid that's blue in color right ? Well the fluid that's in the tc is red like fresh tranny fluid

they most likely put in the no longer licensed by GM the obsolete dexron III...
many repair shops will also do this to increase profit at your expense. these transfer cases require TRAC II fluid and this is available only @ the dealership...about 9 dollars a quart... need 3 qts... actual amount is 2.2 quarts..

now the obsolete dexron III costs 3 dollars a quart ............

remember dexron III is NOT a synthetic fluid....

So would that other stuff mess my transfer case

So would that other stuff mess my transfer case

yes !

do not use any DEXRON III in this vehicle ................

I won't I just hope it hasn't messed anything up I'll put the correct fluid in an get the encoder changed this monday we will see if this fixes my problems

Got my truck out of the shop an it was a wire problem had a few wires that were corroded an plugs that were green an needed cleaning an one wire from the tranny to the transfer case was broke got it all fix for $112 bucks so I'm happy thanks for all the info every one

Got my truck out of the shop an it was a wire problem had a few wires that were corroded an plugs that were green an needed cleaning an one wire from the tranny to the transfer case was broke got it all fix for $112 bucks so I'm happy thanks for all the info every one

Glad you got 'er done Bud. Thanks for posting back.

Got my truck out of the shop an it was a wire problem had a few wires that were corroded an plugs that were green an needed cleaning an one wire from the tranny to the transfer case was broke got it all fix for $112 bucks so I'm happy thanks for all the info every one

where were the wires/connectors corroded ?

the wires small to the transfer case are very fragile and if handled too hard will break easy . these are the encoder sensor position reporting .

most times these are broken if the transmission/transfer case has been replaced/removed ....

did you replace the transfer case fluid ?