ok first off i used the search and i think i know what to do i just want to make sure before i go and spend what little money i have. so my 4wd system does not work. so here is what i think. my vacuum switch is bad. i read that they are cheap and faulty and so it would seam that is what it is. the actuator under the battery holds vacuum. and the box that clicks in the cabin of the truck clicks. and the lights flash and work but it is not changing to what i select. and i founf the hose that goes to the actuator and it has vacuum but does not seam to work for engaging my front axil. well it does but it wont disigage it. i mean that when the actuator is pluged in the switch in the dash is in 4hi and the truck is in 4hi. but i press 2hi and the dash switch does not change and the front axil is still in 4hi. so what makes the vacuum change for ingaging and disingaging the fron axil? thanks so much

 

If the transfer case does not shift, the front axle will not disengage... Have you tried disconnecting the battery for at least 15 minutes to see if the TCCM will reset?

 

yes i tried that and it did not change any thing. so could it be that it might not be the vacuum switch and it could be the "TCCM"?and as far as i know the tccm works it clicks when you push the button.

 

The vacuum switch relies on the transfer case to shift properly. I am not saying that it is your TCCM as it could also be your encoder motor that is at fault.

What 4wd system do you have? NV233 == 3-button switch in dash. NV236 == 4-button switch in dash w/ auto4wd mode.
(and man am I getting sick of asking that question...)

 

yea i have read the posts and you are the saving grace. but i have the 3 button switch on the dash. but the funny thing is id did not work when i got it then it did now it does not . what does that tell you. but here is what i know

1. tccm works(it clicks and so i think it works)
2. vacuum actuator works(it holds vacuum)
3.transfer case i have heard when the system did work it engage and i used 4wd and it worked
4. so that leaves the encoder motor and the vacuum switch. are those both things that go out? i read that the vacuum switch was $25 dollars not to bad and i dont know how much the encoder is but should i replace those to things.

what do you think?
thanks so much

 

The absolute first thing you should do is diagnose the problem. Your works today gone tomorrow description is a bit lacking in substance. It shows that you have an intermittent fault which could be any number of things.

Take a look at the OBD2 Non-Automatic Transfer Case Diagnosis thread in the DIY section. Access the TCCM and watch the lights on the dash switch. If an encoder fault is detected, then you will likely have to replace the encoder. It is expensive just so you know.

 

well thanks i will do what the DIY says and tell you what i get. if i may ask where is a good ground place to ground the wire? thanks