96 Yukon 2d 4wd pissin me off!!!

[bassxlr8r]

I have the push button 3 position 4wd, which worked perfectly until recently. So I was pulling out of my garage and somehow the 4wd engaged itself, I put it back in 2wd and went on my way. A couple of days later, it did the same thing again. I got to work one day, and when I shut the truck off I could hear what sounded like the transfer case actuator (just guessing, couldn't determine exactly where it came from) moving back and forth for like 15-20 seconds, and then it stopped. Shortly after this, the indicator lights on the 4wd selector went out altogether. I checked the fuses and #2 20a T case fuse was blown, so I replaced it, nothing. After this, I thought it was the switch, so I got a used one and went home excited to have 4wd again. Put it in, nothing. Did some more research, and decided to try a new actuator since I read so much about their failing. I got the non-thermal actuator and harness, and just crawled under it to replace and I'll be damned if it hadn't already been upgraded. I checked the connections to make sure it was still getting power and it was. Tried plugging the new one in, still nothing. The switch has power to it also, and all three indicator lights come on when I start, but immediately go off with the rest of the startup dash lights. Does anyone know of anything else I can test/check? Should I try another switch? Please help, it's .4 degrees here and I am finally getting the feeling back in my fingers. Wish I could get the feeling back in my front tires. Thanks

 

[loulblades]

When you heard the actuator acting up did you notice if there was any noise (relays) coming from under the dash?

The TCCM (transfer case control module) is located under the dash attached to the steering post.

If there was no relay activity then it sounds like a short providing power to the actuator.

I wouldn't rule out the (used) switch because it can cause fits.

I find it interesting that you heard the actuator running after you turned the truck off unless the person who did the upgrade connected to a hot source instead of a IGN source (the brown wire on the actuator connector).

 

[ravingmadman]

I find it interesting that you heard the actuator running after you turned the truck off unless the person who did the upgrade connected to a hot source instead of a IGN source (the brown wire on the actuator connector).

+1. If someone replaced it, it might not have been out of the goodness of their heart. They probably had issues with it too, and butchered it trying to fix it. You need to try to get the wiring back to stock, if it isn't already. Figure out what's hot with the key off.

 

[bassxlr8r]

Well, now after messing around with it for a few days I have put the original switch back in. I verified the wire that the actuator was tied into as ignition. They used a Scotch-Lok that still had connection but looked like hell, so that was removed and soldered. I can put the truck in Neutral and engage 4lo, and the front actuator engages so I guess that it's working properly. Both 4lo and 4hi lights come on. After hearing this, I don't think the sound I heard after the truck was off was the 4wd actuator. It was more of a zzzzt-zzt-zzzzt motor type of sound (definitely not door locks though). The actuator engaging sound is much more solid. The steering is heavier and lower gear, but I can't really tell if the front wheels are pulling at all and I don't have a lift to check it. When the truck is in gear, I get no response whatsoever from the switch and after I disengage, all lights go off again. Except the service engine soon light that came on while doing this (went back off today). Is there a way to test/troubleshoot the TCCM? I noticed that in the diagnostic guide you sent me Lou, that it has a few things about the CTSY light fuse. Mine has been blown for a while (not as long as no 4wd, though if I remember right). When I replace it, it works fine until I drive it for a few minutes then pops again. Is there a way this could be related? Thanks for the help. Thinking this is going to get expensive.....dammit.

 

[boat_junkie]

I have an 96, same set up. One of the wires is shorting out. Had to remove the selector motor and leave the selector shaft exposed. Now I manually need to wrench the shaft to engage 4WH, 4wL and 2WH. I kept blowing fuses everytime I tried to push button select. Does this issue sound similar to yours? What is the pn of the updated harness??

 

[bassxlr8r]

Finally got this fixed. Tried using a diagnostic walk through and couldn't get any response. Ended up buying a used TCCM, which allowed diagnostics. Using this I narrowed it down to the transfer case encoder motor, which I replaced and everything works perfectly now. Probably could have figured this out much sooner if I would have realized that there were two separate motors involved in engaging 4wd. When anyone suggested "motor", I assumed they meant the front differential. sad. But, now I know. And knowing is half the battle.