My autotrac transfer case is locked in 4low. The LED on the 2hi, Auto and 4hi will blink if selected, but does not disengage the transfer case. I do not hear the encoder motor trying to shift the case, so I am guessing either the motor is not getting power, the motor is shot, or the gears within the case are physically jammed. I tried all methods of disengaging the case, including attempting shifts in neutral, slow crawl shifting, and cycling between forward and reverse.


During my research, I have found posts by dmaxalliTech, hoot and others describing the problems with the encoder motors and transfer case switch controls. One promising topic (http://dieselplace.com/forum/forum_posts.asp?TID=277&KW=encoder+motor) detailed how "the module may be in a mode that will not allow any shifts or updates for the software or calibrations". The remedy is to pull the TREC fuse for 30 seconds and reinstall which will allow for operation. I understand that this information is for 2003 vehicles, so it may not apply to my 99 K2500. If so, is there an alternative solution to unlock my transfer case so I can take it to the dealership? If there is a TREC fuse, how do I identify it? I have a 20a 4x4 fuse and a 20a Tfer case fuse in the cabin, and an ECM-B and an ECM-I fuse under the hood, but no TREC fuse that I can see.


Any other suggestions would be greatly appreciated.


Thanks for your help.


BTW - First Post!

You can check the 4Wd and TCase fuses. Check connectors to the front axle and encoder motor. If those are ok you'll need to check for codes with a Tech2.

Is there a way to disengage the 4low or am I stuck until I can get a tech2 on it?

If you pull off the encoder motor there is a shaft, but how far and which direction to turn it, I don't know. There are no detents because the motor itself locks in the proper position when shifted. It would be safest to get any codes first then diagnose from there.

The article I cited talked about removing a fuse that would reset the driveline ECU, which would allow shifting. Does this apply to only 2000+ or could there be an equivalent solution for me?


I'm really in a bind here. I can't get the thing out of my garage to read the codes - 4low is the wrong gear to be stuck in.

http://www.dieselplace.com/forum/uploads/tn_gear_and_sensor.JPG


Here is the sensor and the gear it mounts on inside the encoder motor. assuming that is the problem


oh wait....your might be a bit old..sorry


get the codes first, like SID said

That TSB is for 03 trucks but it wouldn't hurt to remove the fuses I mentioned above for 30 seconds to see what happens.

I removed the 20a T Case (#2) and the 20a 4WD (#24) fuse located in the cabin for a minute or so with no luck. I don't know which fuse to pull under the hood, so I didn't explore.


As for the codes, I am not sure if the cable I have is compliant with my truck. I have an ISO9141 cable and have been researching to see if this cable will work for my application. I also have some freeware by scantool.net that should work if I don't short out my ECU in the process. Perhaps there is an easier way to read the codes?


Edit - Found code P1810 (TFP Valve Position Switch Circuit/ Transmission 4-Wheel Drive Low Indicator Short Circuit To Battery)Edited by: SuperTuscan

Makes me glad I have a manual lever on the t-case.