05 Yukon 4wd issues

[WhiteT]

A month or so ago, I would drive for a mile or two and would get a service 4wd message. Truck would be stuck in 2wd, I could turn the key off, then back on, switch to 4wd and everything would work. My research shows this is likely to be the encoder sensor. Well, I haven't gotten around to replacing it yet. A few days ago, I started the vehicle up, the selector switch ran through its normal sequence of flashing all its lights but nothing lit up after that. The truck ran fine in 2wd. I disconnected the battery, let it sit for a few minutes, plugged back in and it worked fine. Yesterday it did it again. Disconnected battery, reconnected it but it did not solve the issue this time. Pulled the 4wd fuse out of the fuse panel inside. Reinserted fuse and everything worked. Today however, same problem, but pulling the fuse and disconnecting the battery is not fixing it. Did the encoder switch finally go bad? I'm leaning toward this, however when the service light would come one, the selector switch would still be lit up. The service 4wd message comes on now, even with the key on, engine off. Anyone ever experience this before? Tia

 

[SLCHOE]

A month or so ago, I would drive for a mile or two and would get a service 4wd message. Truck would be stuck in 2wd, I could turn the key off, then back on, switch to 4wd and everything would work. My research shows this is likely to be the encoder sensor. Well, I haven't gotten around to replacing it yet. A few days ago, I started the vehicle up, the selector switch ran through its normal sequence of flashing all its lights but nothing lit up after that. The truck ran fine in 2wd. I disconnected the battery, let it sit for a few minutes, plugged back in and it worked fine. Yesterday it did it again. Disconnected battery, reconnected it but it did not solve the issue this time. Pulled the 4wd fuse out of the fuse panel inside. Reinserted fuse and everything worked. Today however, same problem, but pulling the fuse and disconnecting the battery is not fixing it. Did the encoder switch finally go bad? I'm leaning toward this, however when the service light would come one, the selector switch would still be lit up. The service 4wd message comes on now, even with the key on, engine off. Anyone ever experience this before? Tia

Yes, most likely. Our trucks have this issue. Symptoms range from:

No lights at all
Stuck in Neutral
T-case jumping out of 2wd and into 4 hi or showing 4-lo but really in 4hi.
Blinking LEDs

Your Encoder motor position sensor is failing.

The motor itself is about $400-600

The sensor that is the actual failing part is ~$40

I do them all the time. It's easy.

http://www.fullsizechevy.com/forum/...-encoder-motor-sensor-replacement-w-pics.html
http://www.amazon.com/Dorman-600-120-Transfer-Motor-Encoder/dp/B004GBAPC2

 

[WhiteT]

thank you for the reply. Today it was stuck in 4 low. pulled the fuse for the 4 wheel drive and was able to get it back into 2 wheel drive. looks like I will have to replace this sensor before I get stuck in 4 wheel drive low for good.