2002 tahoe z71 Service 4wd light on, no blown fuses, new selector switch.

[dougo]

I took mine to a local shop and for small service charge he hooked up his snap on scanner and said the encoder was bad , i found the instructions on line and changed it my self its a common issue i have done it twice , If you are able to find an app that can do it please post details the 2nd time mine failed it dropped the transfer case in neutral i was able to get it in to auto and drove it 800 miles
You can replace the module it self located inside the motor you can get a Dorman for 50 bucks on ebay
the module tells the computer what position the transfer case is in small venerable resistor

 

[2591tdj]

Yea it drives perfect. I'll see if everything is connected, I just ordered a scanner so I can use the app scottydogs suggested, should be at my house on Tuesday so if it's not a faulty ground or unplugged harness Ill give it a scan.


I'll look into an encoder motor now but I just bought the truck a week ago so if it's expensive I may have to put fixing 4wd on the backburner

Replacing the transfer case range select position sensor, ACDelco #88962315, fixed my similar problem. It’s an easy and inexpensive fix. It’s located almost under the driver’s seat. I sealed all around the replacement one with RTV as moisture had been getting into the old and causing it to malfunction.

 

[Ialsofkdyourdad]

Definitely recommend getting the 4x4 codes before doing anything. There are myriad issues that can cause the Service 4x4 message.

If you do get to the point of changing the encoder motor on the transfer case, be sure to check which motor you need by removing the old one before ordering. Some mate with a splined shaft and others mate with a shaft with two flats. Yours is about the year that the transition was made.

View attachment 272117
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Thanks i was confused why the same year had different parts

 

[Ialsofkdyourdad]

I took mine to a local shop and for small service charge he hooked up his snap on scanner and said the encoder was bad , i found the instructions on line and changed it my self its a common issue i have done it twice , If you are able to find an app that can do it please post details the 2nd time mine failed it dropped the transfer case in neutral i was able to get it in to auto and drove it 800 miles
You can replace the module it self located inside the motor you can get a Dorman for 50 bucks on ebay
the module tells the computer what position the transfer case is in small venerable resistor

I'll probably just buy the whole encoder motor assembaly

 

[Ialsofkdyourdad]

Replacing the encoder motor fixed my similar problem. It’s an easy and inexpensive fix. It’s located almost under the driver’s seat. I sealed all around the replacement one with RTV as moisture had been getting into the old and causing it to malfunction.

OK good idea I'll deffinatly put that on the gasket

 

[Fless]

I didn't use any sealer on my gasket; it's not really part of the instructions and mine didn't have any dirt or moisture intrusion. If you do end up changing the encoder motor -- and I'm not really certain that's your problem -- save the thick plastic gasket off the old one and re-use it, unless it's messed up. When you pull off the old one to check the shaft style you'll be able to tell if it can be reused. They're usually in good shape.

And don't be tempted to "test" the new encoder motor without it being bolted up to the transfer case. It's shipped with the splines in a specific position, usually neutral.

 

[Ialsofkdyourdad]

Hey I got a Bluetooth scanner for it what app will read c codes?

 

[Ialsofkdyourdad]

5he one previously suggested isn't finding them

 

[Ialsofkdyourdad]

Found a scanner app that worked with the truck pulled up a bunch of codes but alot of them were test not completed, but I have a C 308 which I think is a transfer case code?


http://imgur.com/a/b06tPry


That's everything the scanner pulled up

 

[Scottydoggs]

Found a scanner app that worked with the truck pulled up a bunch of codes but alot of them were test not completed, but I have a C 308 which I think is a transfer case code?


http://imgur.com/a/b06tPry


That's everything the scanner pulled up

will that app clear the codes? if it can, clear them, then see what comes right back. a lot of times the codes are stored, some could be years old and had been fixed already.

whats the app you found? i like putting these things in my pocket lol