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

 

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elett, Fort Wayne, IN, January 05, 2014, 06:12
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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.

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    pushrod January 05, 2014, 06:29
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    Scan test needed on the transfer case module. Anything else is wasting time and money!

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    elett, January 05, 2014, 06:45
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    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

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    pushrod, January 05, 2014, 06:53
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    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!

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    elett, January 11, 2014, 11:44
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    Pushrod, You have any further input you could offer

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    pushrod, January 11, 2014, 15:16
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    Yes but to do so at this point would be moot.

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  • Answer #2

    G. T. Service Center (3149 Answers) , Stephenville, TX - (254) 638-3236
    ProfessorG January 05, 2014, 07:59
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    Just asking; Do you mean the encoder motor instead of the encoder switch? There is a sequence to follow when installing it.

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    elett, January 05, 2014, 10:20
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    I installed the transfer case range selector position sensor p/n 89059276

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    ProfessorG, January 05, 2014, 10:27
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    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.

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    elett, January 05, 2014, 10:56
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    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 ?

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    ProfessorG, January 05, 2014, 11:16
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    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.

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    elett, January 05, 2014, 13:28
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    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.

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    ProfessorG, January 05, 2014, 13:36
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    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.

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    elett, January 05, 2014, 15:12
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    Tanks again, I will post the outcome as soon as I get to the bottom of it.

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    ProfessorG, January 05, 2014, 15:16
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    Good Deal.

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    elett, January 11, 2014, 02:10
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    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?

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    ProfessorG, January 11, 2014, 07:13
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    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.

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    elett, January 11, 2014, 11:40
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    Went to store started working again..... Leaving to go visit a friend quit working again...any ideas

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    ProfessorG, January 11, 2014, 14:59
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    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.

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