Hey guys, my 4wd has stopped working, the 4wd button constantly flashes, but doesn't shift in, I checked my vacuum actuator ando it holds a vacuum, and is constantly sucked in when the truck is running, I hear the tccm click when I try to engage it, any ideas? My service 4wd is also on, thanks

 

'Service 4wd' means that you have the NV236 4-button 4wd system and also means that you have a failure code present that should be read to determine why the system is locked up.

If the actuator is always sucked in and you are not in 4wd presently, then you have a problem with the vacuum solenoid located on the firewall near the distributor. Either the lines are incorrectly routed or the solenoid is malfunctioning.

 

I forgot to mention that it is stuck in 4wd and won't shift out, if the actuator is sucked in is it in 4wd or 2wd?

 

If the actuator is pulled in (under vacuum), then the system is in 4wd.

You really should get the TCCM scanned for codes before doing anything else as the truck is trying to tell you what it thinks is wrong.

If that just isn't in the cards for you and you have the time to screw with it... Pull the passenger kick panel & disconnect the TCCM electrical connectors & check them for corrosion. If present, clean the corrosion from both the pins in the TCCM & the female terminals in the connector. Once cleaned, coat the connector with dielectric grease, reconnect, & see how things work. Just to warn you, this might not be a permanent fix.

There are more trouble shooting tips in the Tech Article (DIY) section. Take a look at the index link in my signature & look for links in that thread with NV236 in the title.

 

I tried scanning my,car at autozone but no 4wd codes show up? Do I have to take it to a dealer?

 

Autozone's scanner likely is not capable of scanning the serial bus networked devices such as the NV236 TCCM. That will require a bi-directional communication capable scantool. There are many scantools that have this capability, but finding a shop with one that also knows how to use it may be a feat in and of itself.

 

This is why I belong to this forum, people are nice and know way more than I do, but I did pull out the tccm and one wire on the big harness looked jimmy - rigged, when look at the harness straight on, it was the uppermost left hand corner wire, it had quite a bit of copper rust ( the blue stuff that I call it) so I cleaned it up the best I could and finally it got back into 2wd with some bit of backing up, forward and curse words, Haha I bet my neighbors thought I was drunk, but my service 4wd light is still on, so next I guess I will take it to my trusted mechanic and see if he has the scanner required for the tccm. Will the scanner read exactly what is wrong, or will it be the general location?? Thanks so much swartlkk

 

The code will give directly.

Corrosion on a pin is never a good sign. Even cleaning the pin & terminal may not allow it to properly make contact. I have had to replace the affected terminal before due to corrosion eating up the inside of the terminal. Most of the time I just grab a terminal from a junkyard connector of the same size. Others have bought all new harnesses.

NAPA carries the terminals so you can crimp on a new one if you find the proper PN. I believe I have posted it in the past, but posting from my phone such as I am doesn't allow me to search very readily.