encoder sw. replaced, still no 4 wheel drive or lights on selector switch on 2002 GMC Envoy

Help! I replaced the encoder switch as suggested by my GM dealer. I still have no 4 wheel drive options nor any lights on the selector switch. The selector switch lights do work when first started then go out also the service 4 wheel drive light stays on.

by in Fort Wayne, IN on January 05, 2014
3 answers 33 comments
ANSWER by on January 05, 2014
Scan test needed on the transfer case module. Anything else is wasting time and money!
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COMMENT by on January 05, 2014
Thanks Pushrod... I took it to GM dealer for diagnosis.... it cost me $80.00 GM mechanic told me the encoder switch needed replaced which I did my self , should have the GM mechanic known that the TCCM needed scanned as part of their $80.00 trouble shooting? any idea location of the TCCM. I'm just wondering if the GM Mechanic is doing his job or just throwing my money at it. I could of done that my self haha
COMMENT by on January 05, 2014
That's a good way to put it! Frankly i would take it to a good independent shop for testing! One that has an up to date professional scanner. I find/think we try a little harder than the dealer's commission salary techs.....or employees rather! Now that is just MY opinion!
COMMENT by on January 11, 2014
Pushrod, You have any further input you could offer
COMMENT by on January 11, 2014
***Yes but to do so at this point would be moot.*** ****AS ALL THE WASTED BS ON THIS PAGE IS INDICATIVE OF****
ANSWER by on January 05, 2014
Just asking; Do you mean the encoder motor instead of the encoder switch? There is a sequence to follow when installing it.
COMMENT by on January 05, 2014
I installed the transfer case range selector position sensor p/n 89059276
COMMENT by on January 05, 2014
That is not the 4x4 encoder. The encoder is on the transfer case and controls the shifting movement. The GM tech might have given you good information, but you replaced a part that has nothing to do with the encoder. That part will not fix the 4wd.
COMMENT by on January 05, 2014
understood thanks... their are three parts to the encoder motor (1) being the (ACTUATOR), (2)the (SENSOR)p/n 89059276 which is installed just in front of the actuator (3) the (INSULATOR)"gasket" p/n 88996636. All three together make up the encoder motor which install via. the spline shaft perpendicular from the transfer case. The GM mechanic advised that the sensor was bad. Any suggestions for the home fix ?
COMMENT by on January 05, 2014
The encoder is not just an actuator, It has a circuit board that commands the actuator to different positions via the transfer case control module. Just looking up the parts involved will not explain the function or operation of this system without the experience and knowledge of repairing several issues over the years. If you had a Tech2 scan tool and knew how to command the functions of the transfer case control module, you then could see what was functioning properly and what was not. In a lot of cases the power control to the actuator has been compromised, causing no actuator function. So that being said then you would have to be able to diagnose and trace circuits pertaining to the operation and function of the 4wd system. Not trying to be rude but if you don't have the equipment or knowledge of this system, you might cause more problems than what you've started with.
COMMENT by on January 05, 2014
ProfessorG, Thanks for the response, no not at all thinking you are being rude with your response. I just figured taking my vehicle to a GM dealer mechanic they could of diagnosed my issue better then was done. I would assume they would of used their "Tech 2 scan tool" via the TCCM before they advised me to replace the sensor, which I did. Now I'm setting here in my living room, no 4x4, watching it snow for the last 12hr., with no sign of let up for the next several hours. Thought I could get some good sound advise on this thread, which I guess I did from "Pushrod". Basically just a shade tree mechanic trying to save a little money and having the pleasure of repairing my own vehicle like the good o'le days.... That being said if you have any of that good down to earth technical information it sure would be welcome. Already making appointment with my local neighborhood mechanic probably.
COMMENT by on January 05, 2014
The dealer should know but they go through hands quite often with their pay scale. The mech u got May not have the same ability as one who has been working on these issues as much and maybe made a good guess. Sorry but it's not always the same fix with the same symptoms. Sorry but was trying to stress that it's not that easy to tell you what to fix. When we have learned the mistakes already.
COMMENT by on January 05, 2014
Tanks again, I will post the outcome as soon as I get to the bottom of it.
COMMENT by on January 05, 2014
Good Deal.
COMMENT by on January 11, 2014
I dropped it off at my local independent shop. They advised that their is a service bulletin that states when the position indicator switch is replaced on a 2002 and only on a 2002 model envoy it has to be reprogramed, which they did. It worked fine and all was back to normal for two days , now it's not working again and acting the same way. Any suggestions? What caused it to fail again?
COMMENT by on January 11, 2014
It's not easy to sit here and make an educated guess without seeing the scan data to back me up. My thought is the programming worked initially and then quit after two days makes my opinion lean toward the control module to be the issue of the fault. Just an opinion of the information I have been given.
COMMENT by on January 11, 2014
Went to store started working again..... Leaving to go visit a friend quit working again...any ideas
COMMENT by on January 11, 2014
Wow plenty of ideas, just want to put my scanner on it and read it to see which part is not responding. Either the module is sending the information to the encoder and the encoder is not/or not able to switch positions, possible motor issue, OR Vise-Versa, the module has a glitch and will work intermittently, possible bad connection, bad circuit board, cold solder joints. The scan tool will give that info, but knowing how to read it is another. That's my dilemma, I want to give you the right answer, and can only guess.
ANSWER by on June 26, 2014
i have the same problem.the 4 wheel drive acuator motor within the transfer case is bad.it is a 100 dollar part.ive tried everything else too.
COMMENT by on June 26, 2014
What is the fault code, A-B circuit fault maybe?
COMMENT by on June 29, 2014
It's been working fine now since March. Did nothing else to it thinking it could have been a ground issue won't know till winter when I need it again lol
COMMENT by on September 28, 2014
hi I saw this thread and I'm having an issue with my 4 wheel drive so I throw this question out there. my truck got stuck in 4 wheel drive and wouldn't go back into 2 wheel drive I replace the encoder motor (it was seized up) and it went back into 2 wheel drive. Fixed right? Not so fast now the 2wd light is illuminated and when turning knob to go into 4wd nothing happens, the light that would normally blink when going into 4wd does not even go on and the 2wd light stays lit. All lights illuminate when starting truck so don't think it would be the switch. Was thinking of trying to replace the TCCM but am hesitant based on price if it doesn't fix it and would like be more confident instead of throwing money and time at it. Here are the codes that came up on the scan. Anyway to tell what I should change next or is it a shot in the dark? C0201 anti lock Brake relay U1041 lost com brake system C0306 motor a/b malfunction C0321 transfer case lock malulation c0327 encoder circuit
COMMENT by on September 28, 2014
Check and clean the frame grounds at the cab bushings, under battery frame and the upper 'A' arm. AB circuit is mostly a ground issue
COMMENT by on September 28, 2014
thanks, did the one under drivers side door already will try other one. Where is the upper A arm one located?
COMMENT by on September 28, 2014
Behind of the l front tire.
COMMENT by on October 04, 2014
Changed the encoder motor, 4wd actuator and selector switch now and still no luck. No sounds when turning selector switch to 4lo. There should be a significant sound when doing so correct? TCCM bad??? Not much more to check... Thanks if anyone can help
COMMENT by on October 05, 2014
There are several things to check and verify. I do these all the time and usually have ground issues with the a/b circuit. Update programming the tccm is another possibility. If you replace it then it will need programming as well. Just changing parts is not necessarily going to fix the issue.
COMMENT by on October 05, 2014
Professor my question is does it matter what state the 4 wheel drive on the truck is in before installing the new encoder motor? when I installed the new encoder motor my truck was locked in 4 wheel high. Does it need to be in 2 wheel drive high before installing motor or doesn't it matter? Thank!!!
COMMENT by on October 05, 2014
A new encoder should be set in the neutral position when installed.
COMMENT by on October 05, 2014
Could this be my problem? If so how do I correct?
COMMENT by on October 05, 2014
Have the codes ever been cleared during this.
COMMENT by on October 05, 2014
Not fully that I know for sure. Took it to one store and no codes showed up took it to another and codes did show up. Most recent nine showed up.
COMMENT by on October 05, 2014
Needs a Tech2 or professional scan tool. You're wasting money without it. Not a DIY without the proper equipment. Sorry
COMMENT by on October 05, 2014
Sorry for keep going on.....Are you saying auto zone, advanced auto are not repetable for code scanning?
COMMENT by on October 06, 2014
They can't any codes except generic engine codes. They can't read the seperate modules, 'IE', tccm, body, abs, SRS, etc,
COMMENT by on January 05, 2015
My switch started to malfunction again starting November , has worked fine since June. Just a thought has anyone found the cold to be a factor? I think I found the problem, removed the front axle actuator, took it apart and found the circuit board contaminated with grease which caused a high resistance along with slowing down the movement of the actuator with below freezing temperature. Cleaned contact area and reinstalled. So far so good.

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