I have a 99 Blazer with RPO of NP8 which I believe is the NV236 correct?

So, I drove into a field starting out in AWD and got stuck. Tried to go from AWD to 4HI and it did not engage. For a brief second or two it said "service 4 wheel drive" so I put the trans in Neutral and tried 4lo about 4 or 5 times until it finally did engage and I was able to get out and drive home about a block because it's stuck in 4LO and will not go into AWD, 2hi, or 4hi. The 4lo works fine, just won't disengage. Also, the "service 4 wheel drive" light is no longer on. I used a scan tool and only got an 02 sensor code.

Less than 20K miles ago I had a new encoder motor and 4x4 dash switch installed because it would NOT go into 4HI or 4LO. I have rarely used 4 wheel drive since installing these parts except AWD in the snow here in Michigan.

I've read a lot about the vaccuum lines but have not checked those and not sure exactly how to check them. I understand on this system there is one under the battery tray and another on the firewall? So how do you check them and how do you know if they are bad?

I plan to check The TCCM and I understand is behind the "kickplate" on passenger side, so once I do get to the TCCM what is the procedure for checking it? Do you just clean the connectors and apply dielectric grease and replug and try again?

Any other help would be appreciated and photos if you have any.

 

Hi , There should be a code stored in the TCCM , but you won't be able to read it with a OBDII reader unless it is an expensive one or you have access to an OBD terminal....I would recommend you have the code read....It may point you in a direction for trouble shooting.