Intermitent 4wd

[03TAHOEPU]

Hey everyone, I'm new here and looking for help on a problem I've had for several years now. I have a 2003 chevy 2500hd, allison 4wd. I have not beenable to rely on my 4wd because the lights on the selector do what they want. Most of the time I have no 4wd. If i do the 2wd light stays on and dash displays check 4wd. I never get a code because when you turn the key off it clears. (not a hard set code) You never know wich lite will be lit, could be 4hi, 2hi, 4lo. or neutral light on. never shifts into what is displayed and you can't get it out of what it's in. Sometimes if you put truck in drive and start to move you can back to 2hi , drive down the road a ways and check 4 wheel drive comes on. this thing has a mind of it's own. Switch seems ok and I'm wondering if the NSBU can be bad. Or how about the speed senser. Any help would be appreciated

[Toadz]

Bump. I've been dealing with this problem for quite sometime but it hasn't bothered me enough to get it resolved. Most of the time I am still able to use the different modes but the lights will just go out and the Service 4WD light will stay on until the key is turned off. I've heard it could be a bad solder in the selector circuit board to a bad ground on the transfer case.

[oldschool327]

Is the actuator corroded on the transfer? Most guys neglect the underbody and these little guys like to give problems after awhile of crap stuck to them. Just a thought

[Z45]

99 thru 04 ish trucks are noted for shoddy Delphi electronics. The dash switches go bad, or the motor in the transfer case does.

 

Would be wise to take it to a GM dealer and find out which is the problem. It could be expensive throwing parts at it if its just a simple $40 dash switch which it often is.