Service 4X4 on screen 2005 Chevy Tahoe

I'm told that it could be the switch for the 4X4 system ( on the dash ), or the Encoder motor sensor or the encoder motor on the transfer case. The service writer at the GM dealer says that I cannot replace the Encoder motor/sensor myself because once you remove the old one and install and plug in the new one it has to be programmed first. Is this true? The dealer wants to charge $218.00 in labor to replace the motor plus $557 for the new part (if that is indeed the problem). How will they determine whether it is the Encoder Motor, the sensor, or the switch on the dash? Will they simply plug in a scanner and read codes or will they actually do electrical testing on each part and measure resistances? I'm trying to save as much money as I can. I found the OEM replacement Encoder motor/sensor for $249 on eBay. It's held on by 2 bolts, can't take more than 10 - 15 minutes to change myself. Can I change it myself and then drive it to a shop with a scanner to have it programmed? Any help would be appreciated.

I'm told that it could be the switch for the 4X4 system ( on the dash ), or the Encoder motor sensor or the encoder motor on the transfer case. The service writer at the GM dealer says that I cannot replace the Encoder motor/sensor myself because once you remove the old one and install and plug in the new one it has to be programmed first. Is this true? The dealer wants to charge $218.00 in labor to replace the motor plus $557 for the new part (if that is indeed the problem). How will they determine whether it is the Encoder Motor, the sensor, or the switch on the dash? Will they simply plug in a scanner and read codes or will they actually do electrical testing on each part and measure resistances? I'm trying to save as much money as I can. I found the OEM replacement Encoder motor/sensor for $249 on eBay. It's held on by 2 bolts, can't take more than 10 - 15 minutes to change myself. Can I change it myself and then drive it to a shop with a scanner to have it programmed? Any help would be appreciated.

this does not need to be programed...the question is what is your problem ????also did the dealer pull the DTC drive train codes ??
or is he just guessing at YOUR expense..

log in with the drive train DTC and your issues with the 4X4 ....then answers can be given...you are not the first with this problem...

no programing is required...it could also be the 4x4 control circuit next to the dash 4x4 switch...

I am having this same problem and I am not sure what log in with the DTC means. I am hoping I don't have to spend a lot to get this fixed. Thanks

I am having this same problem and I am not sure what log in with the DTC means. I am hoping I don't have to spend a lot to get this fixed. Thanks

report what the DTC is which , is the failure code of the drivetrain...this means you will need a gm specific drive train capable scanner...

hey reading the past post i think i can put some insight on what your problem is.if you are getting a message that say service 4x4 and you can see the all the lights on you 4x4 buttons are not light up you are going to need a new 2 wd 4wd switch sensor it comes as a whole button cluster the cost of this part a chevy is 90.00. now if you get a message that says service 4x4 and stability system disabled , and when i say stability system disabled i mean like if you where to push your traction control off ,you will know if you have this message cause you will not be able to turn the traction on or off and the the t/c light will be on in the upper left corner of your dash .if this happend with the service 4x4 message you will need to get a encoder motor that is on the side of the transfer case this part will cost 450 at the chevy dealer the motor also comes with the sensor .if you you have access to a good code reader and not some cheap one from your local parts store i am sure you are going to get the c0327 code that means you are going to need that encoder motor .i see this problem at my shop with at least 50 chevy trucks a year this is a very known problem with chevy they just do want to say anything about it so they dont have to recall it .both of these parts you can change your self in a few hrs ,you also do not have to program the encoder motor . ihope this helps you guys out .

also if you start to experience any type of ruff shifting skipping gears wont down shift its that encoder motor dont worry you dont need a new tranny dont let anyone tell you that you do

cory e
gm certified mechanic

hey reading the past post i think i can put some insight on what your problem is.if you are getting a message that say service 4x4 and you can see the all the lights on you 4x4 buttons are not light up you are going to need a new 2 wd 4wd switch sensor it comes as a whole button cluster the cost of this part a chevy is 90.00. now if you get a message that says service 4x4 and stability system disabled , and when i say stability system disabled i mean like if you where to push your traction control off ,you will know if you have this message cause you will not be able to turn the traction on or off and the the t/c light will be on in the upper left corner of your dash .if this happend with the service 4x4 message you will need to get a encoder motor that is on the side of the transfer case this part will cost 450 at the chevy dealer the motor also comes with the sensor .if you you have access to a good code reader and not some cheap one from your local parts store i am sure you are going to get the c0327 code that means you are going to need that encoder motor .i see this problem at my shop with at least 50 chevy trucks a year this is a very known problem with chevy they just do want to say anything about it so they dont have to recall it .both of these parts you can change your self in a few hrs ,you also do not have to program the encoder motor . ihope this helps you guys out .

also if you start to experience any type of ruff shifting skipping gears wont down shift its that encoder motor dont worry you dont need a new tranny dont let anyone tell you that you do

cory e
gm certified mechanic

cory your troubleshooting this like some repair garage in the remote mountains of mexico ! you know or should know since you are a professional gm trained tech that the drivetrain codes need be pulled to determine what need be done ...

I welcome you to the forums but give us some usable input ..not typical backyard mechanic guessing...

wow !!!!!! so again i have see this problem over 50 times a year. the only thing that is going to set those messages off is what i talked about ! but forget about trying to help some people out. its because of jackasses like you people are out there spending thousands of dollars trying to get something fixed when all they needed was a $300 part and 20 min to put it in
i can already see that there is going to be a bunch of dumbass hicks on here so sorry for trying to help !!!!!!!!!!!!!!!!!!!!!!!

wow !!!!!! so again i have see this problem over 50 times a year. the only thing that is going to set those messages off is what i talked about ! but forget about trying to help some people out. its because of jackasses like you people are out there spending thousands of dollars trying to get something fixed when all they needed was a $300 part and 20 min to put it in
i can already see that there is going to be a bunch of dumbass hicks on here so sorry for trying to help !!!!!!!!!!!!!!!!!!!!!!!

cory the problem is no testing just guessing...GM has delvoped diagnostics to reveal failures...then the technician using his test equiptment verifies then replaces this defective part , or makes other corrective actions which may not require a part...

your idea of just because I seen this 50 times that means it must be the problem is why we here have reports from owners paying 1000.oo for these repairs..at the dealership .....while others have made these repairs for less than 200.00 by themselves or a non dealership..

My experience is with large computer controlled transportation vehicles that have far greater monitoring / controlling electronics and with the cost of these parts one does not guess but use the computer program to resolve issues of operation in a more precise professional unguessing way..

If you did properly troubleshoot your work at the dealership , I would suspect that you would be fired ....! replacing parts is part of the dealerships profit ...guessing is good for profit !

wow go back and read the firs post i put up . i told you if you are getting the service 4x4 and the traction off light at the same time you are going to get the same code every time .like i said i have been doing this for 20 years every time i see this problem the person pays less then 500 for the fix not 1000s.

c0327 every time !!! encoder motor

wow go back and read the firs post i put up . i told you if you are getting the service 4x4 and the traction off light at the same time you are going to get the same code every time .like i said i have been doing this for 20 years every time i see this problem the person pays less then 500 for the fix not 1000s.

c0327 every time !!! encoder motor


there have been owners that had wiring issues that caused this code...sure with this code 90% it would be the encoder...

With the drive train code given this can then used to help this repairer using troubleshooting proceedures to make the correct repairs..

also if parts are needed where to get them...for a reasonable cost..

I have been having the following problems with my 2005 tahoe intermittantly for over a year
Stability System Disabled
Service 4 Wheel Drive
Traction Control Light on
Sometimes when first starting and for a while after engine would not exceed 1800 Rpms after highway driving this would start to function normal.

I have taken to Chevy twice to get fixed, first they told me a had hundreds of codes so they thought it was my auto car start interfering with it. I had that taken out and for a little while it was ok but I think that was just coincidence. Then i took it back again and they told me still too many codes they don't know what to do.
found this thread and took it in again, this time they said no codes? and we cant replicate. I don't know how that's possible because it's been to the point where all the warning indicators were constant and you cant shift from 2wd to anything else.
Based on Corye advice I told them to just replace the encoder motor and sensor. 1.5 hours and $289 later my truck is finally running like a charm, no warning lights, everything perfect. If his style is "backyard mechanic" it worked for me when nobody else could fix it.
Thanks Cory

I have been having the following problems with my 2005 tahoe intermittantly for over a year
Stability System Disabled
Service 4 Wheel Drive
Traction Control Light on
Sometimes when first starting and for a while after engine would not exceed 1800 Rpms after highway driving this would start to function normal.

I have taken to Chevy twice to get fixed, first they told me a had hundreds of codes so they thought it was my auto car start interfering with it. I had that taken out and for a little while it was ok but I think that was just coincidence. Then i took it back again and they told me still too many codes they don't know what to do.
found this thread and took it in again, this time they said no codes? and we cant replicate. I don't know how that's possible because it's been to the point where all the warning indicators were constant and you cant shift from 2wd to anything else.
Based on Corye advice I told them to just replace the encoder motor and sensor. 1.5 hours and $289 later my truck is finally running like a charm, no warning lights, everything perfect. If his style is "backyard mechanic" it worked for me when nobody else could fix it.
Thanks Cory

with no engagement of 4wd the encoder is highly suspect since it is the weak link doing all the heavy work.

replace the tranfercase fluid every 30,ooomi with or without any 4wd use as this fluid gets damaged from heat and friction.

this will reduce the encoders work load.

other causes holes in the transfercase,fluid damaged to a black color,wires chewed up by rodents, even holes in the encoder motor housing.

the switch on the dash is a common easy fix.re-solder the switch pins to the circuit board or buy new switch..

to bad you couldn't have cory the GM tech work on it . he is good at guessing not testing..

you know their is a testing proceedure for all this ! GM tech at dealership should have done this.

Thanks for the info j cat. I hardly ever use the 4wd, only a couple of times in the worst of snow storms. I have never had the 4wd serviced and I don't do any work on my cars personally.
I will bring it in and have the transfer case fluid changed.
As far as them doing the diagnostics, they did. I just went and checked my records and it turns out I went three prior times, twice to one place and once to another. This last time I went to yet a third place and when they couldn't give me an answer that's when I just told them to replace the encoder.
Just hit 100k in my truck a couple of weeks ago and I'm really happy about having this fixed. This was the only issue I have had over the last 60k miles. Prior to that I had the intermittent steering shaft replaced 2x.
I love this truck and hope I hit 200k with it. This is my 3rd tahoe, I put a lot of miles on them and have traded the last 2 in with around 55k miles on them.

Thanks for the info j cat. I hardly ever use the 4wd, only a couple of times in the worst of snow storms. I have never had the 4wd serviced and I don't do any work on my cars personally.
I will bring it in and have the transfer case fluid changed.
As far as them doing the diagnostics, they did. I just went and checked my records and it turns out I went three prior times, twice to one place and once to another. This last time I went to yet a third place and when they couldn't give me an answer that's when I just told them to replace the encoder.
Just hit 100k in my truck a couple of weeks ago and I'm really happy about having this fixed. This was the only issue I have had over the last 60k miles. Prior to that I had the intermittent steering shaft replaced 2x.
I love this truck and hope I hit 200k with it. This is my 3rd tahoe, I put a lot of miles on them and have traded the last 2 in with around 55k miles on them.

just the other day I was checking out the silverado drive train fluids, and other under body components for condition.

looking at the transfer case encoder motor, I can see how off roading with no shielding to protect it , has caused some to have severe damage to the case.

I' m having these same problems. the service 4 wheel drive came on a few months ago and only comes on now when on long trips.... now the stabilitytrac system disabled was on. It was in 4 wheel drive so i switched it back to 2 wheel drive. is it unsafe to drive it like this?

I' m having these same problems. the service 4 wheel drive came on a few months ago and only comes on now when on long trips.... now the stabilitytrac system disabled was on. It was in 4 wheel drive so i switched it back to 2 wheel drive. is it unsafe to drive it like this?


these vehicles ARE NOT TO BE USED IN 4WD ON SOLID DRY PAVEMENT !

If you have been operating in ANY 4wd position on solid dry pavement , I suspect that your drivetrain must be serviced immediately..

good chance parts/fluids are worn damaged..

I didn't put it in four wheel drive it kicked its self into 4 wheel drive. Is it going to cost a lot of money?

I didn't put it in four wheel drive it kicked its self into 4 wheel drive. Is it going to cost a lot of money?

you must explain better how this is working/not working.

example: as I drive my 4wd tahoe it goes into 4wd from 2wd by itself.

this happens how often ? what speed ? does it go back to 2wd when commanded ?

vehicle description, how many miles? last time 4wd serviced ? how long owned by you ?

you will need a drive train scanner to get the failure code. this requires a GM specific code reader. call for a shop that can read this. thenpost back with all your info. perhaps a simple fix. could also be expensive ..

I have been having the same problems for about 8 months. The backlights work on the switches (4x4 and TC) They both are totally unresponsive. Service 4 Wheel Drive and Traction Control Disabled are always in my dash readout display. i had the codes tested by a GM technician with their laptop computer(newest version). There were no codes, however he was able to make the 2wd, 4hi, and 4low lights come on in the switch module (so I assume that means the switch is fine?). Now... should I just get the "encoder motor" or see if there is a program update or what? He said nothing about any new flash updates "reproggraming" for this. I need an expert answer. The encoder motor is around $250.00 now if I buy online. I should be able to install myself. I really want this fixed.

I have been having the same problems for about 8 months. The backlights work on the switches (4x4 and TC) They both are totally unresponsive. Service 4 Wheel Drive and Traction Control Disabled are always in my dash readout display. i had the codes tested by a GM technician with their laptop computer(newest version). There were no codes, however he was able to make the 2wd, 4hi, and 4low lights come on in the switch module (so I assume that means the switch is fine?). Now... should I just get the "encoder motor" or see if there is a program update or what? He said nothing about any new flash updates "reproggraming" for this. I need an expert answer. The encoder motor is around $250.00 now if I buy online. I should be able to install myself. I really want this fixed.


the problem you have is a dealer tech unable or unwilling to give you the dtc drive train codes.

go to another repair shop that will give you these failure codes.

with the service 4wd Lt on this must have failure drive train codes..

then post back the dtc drive train codes ..with this the forum members will get you going in the right direction..

you have a componet failure not a need for any update !

I' m having these same problems. the service 4 wheel drive came on a few months ago and only comes on now when on long trips.... now the stabilitytrac system disabled was on. It was in 4 wheel drive so i switched it back to 2 wheel drive. is it unsafe to drive it like this?

Hi girl in need,
Service 4x4 ligth comes up on my Yukon 2005 also. Its been flashing for few months. Now, ramdomly car shift to 4x4 by itself while driving. I'm unable to control the transmision mode pushing on the panel 2wd, 4-lo, 4-hi switches. I have been searching and reading coments about this issue. Cause of problem are many. So far, the ultimate solution I found is to go the dealership for a computer/transmission software update before replacing any part and go from there. The new software should give you the right code of what is wrong.
Possible problems are: Low transfer case fluid or insuficient lubrication due to lack of use of 4x4, the panel switch/cluster itself, the 4x4 tranfer case relay, 4x4 control motor in front axel, wiring, or encoder sensor/motor (c0327 code).
I have not seen my stability (Cory_e talks about) or traction system disable light on. So, I hope the encoder is not my problem. And all the lights on the cluster swith ligth up and flash before stoping on the 2WD, so, I hope my problem is not this switch either. And I have not changed/serviced the 4x4 fluids ever. I now have 75K miles on this Yukon.

My research shows that these repairs cost about $800.
If not repaired soon, car could engage in 4x4, and a turn on pavement could damage gears and other parts. That happends to someone I know with a Chevy Z71 Silverado pick-up truck 2003 and the repairs were $2300.!!!

Good luck

Hi, Guys. Thanks a lot for all the great info. I just purchased a used 2005 Tahoe a week ago. The "Service 4WD" message appeared yesterday. No other messages appeared. I selected 4WD, and it went in OK. Just wouldn't come out! I drove around the yard a little bit, reversing direction and gear, and eventually it went back to 2WD. Subsequent attempts to re-engage 4WD failed. The 4WD (HI) button would flash for 15 seconds or so, then extinguish. Upon selecting 4WD, I heard noises down below as it attempted to satisfy the request. Now, when I select 4WD, either HI or Low, the indicator lights stay black and there's no activity. It's as though the computer had locked out the switch panel 4WD functions.

The Tahoe has 93,000 miles on it. It was a fleet owned vehicle. I'm not sure if that's a good thing or a bad thing. I assume it didn't go off road. The undercarriage is cleaner, corrosion-wise, than any of the Tahoes we looked at.

Monday, I'm going to take it in to get the Drive Train Diagnostic Codes read, and have them put it up on the lift and check out the transfer case fluid, then change it, and see what happens.

The used car dealer I bought it from is down in New Jersey, about an hour and forty-five minutes drive each way! He said I have to bring it in for servicing. By the time I do that, I'll be approaching the limits on my one-month, 1,000 mile warranty. Hmmm.

Plus, it's a real drag driving down there, we'd have to take a chase car along, leave the Tahoe there, come home, drive back down, etc., etc. etc. What to do?

have the drive train failure codes read by a shop near you. report the findings here.

If its just the encoder bad then have that work done near home. see if the used car dealer will cover it. keep all paper work.

could be bad wiring. wiring is very fragile on these vehicles. the fuse box underhood wires to the transfercase get damaged very easily.

If the transfercase fluid is black then you should consider getting your money back/return the vehicle. cost can be quite high.

the encoder usually fails because the fluid is black/damaged. this stresses out the encoder. the black is clutch material which in most cases is from operating the vehicle in any 4wd setting on solid dry pavement , also tires of different wear or size . all tires need be worn and rotated to keep at the same size / wear.

JCat:

Thanks so much for your great advice! I'm going out to the car now. I'm going to see if Onstar can read the OBD.

The dealer says he can't trust anybody to not rip him off, so I must drive the vehicle down to Jersey. I wonder what he'd say if I told him I was stuck in 4 Lo??

OK. Onstar ran a diagnostic. Tahoe is experiencing a C0306: Motor A or B Circuit Malfunction. Service within 7 days.

So, not an immediate emergency. The operator handed me off to a diagnostic specialist who said it could be as simple as a loose wire, or possibly a bad TCCM.

Guess I'll call the dealer again and see what he'll do, or won't do.

OK. Onstar ran a diagnostic. Tahoe is experiencing a C0306: Motor A or B Circuit Malfunction. Service within 7 days.

So, not an immediate emergency. The operator handed me off to a diagnostic specialist who said it could be as simple as a loose wire, or possibly a bad TCCM.

Guess I'll call the dealer again and see what he'll do, or won't do.

the transfrcase encoder motor is the weak component. the electronic control module rarely fails. I would say is is the encoder. this can be checked by measuring for a short or open.

the next thing you must do is see what color the fluid is.

should have been some other codes found.

Thanks very much.

Yes, you would expect a 309 if the encoder was bad. That's why I was a little relieved to see an electrical fault. Even if it was the TCCM at $700 a pop! At least the tc wasn't smoked in that event.

But now you've got me concerned. So tomorrow, I'll take it to the car wash and see what their reader says. Also, put it up on the lift and check the fluid, and change it. Although,iirc, they may not stock the special fluid.

Edit:

From the User's Manual:

Dexron®-III Automatic Transmission
Fluid. Look for “Approved for the
H-Specification” on the label.

So:
Wondering what to do if the fluid is fried. Leave it in the transfer case as evidence for the dealer to confirm?

Or: change it and risk his denial?

Thanks again!

upthereinthesky,
Is the dealership you're working with one of our dealerships? Let us know as we would be happy to look into this further.
Best,
Sarah
GM Customer Service

Sarah:

Thanks very much. This dealer is a small, privately owned business. I'm not sure how one would tell if it is a GM franchise. I assume this place is not, as they sell only used cars, and a hodge-podge at that. As a matter of fact, judging by the cars on their lot, they sell mostly Hondas and Toyotas.

Thanks again.

the transfrcase encoder motor is the weak component. the electronic control module rarely fails. I would say is is the encoder. this can be checked by measuring for a short or open.


Thanks, j cAT.

Is there a procedure printed somewhere to show me where the pinouts would be? Or, do I just unplug the wiring harness and check there? It's difficult for me to get to the underside. It would be nice if I could pop a plug up top somewhere to check for a short or open.

the transfercase uses blue GM trac II transfercase fluid. you will need 3 qts. uses 2.25QTS. the fluid should be blue or a gray blue color. if black you will need a complete rebuild.

the TRANSMISSION USES DEXRON VI NOT DEXRON III. DEXRON III was removed in 2006 because it is a damaging acid creating fluid/ poor quality. cost GM too much in warrantee work so they no longer license this spec fluid.

recheck those drive train codes again. the computer module is how the jack up the cost. yes it is very possible its just a wiring problem , cheap if you fix it very expensive if they fix it because they will change everything else first ..you get what I'm saying here !

the encoder could be open or shorted. could be the encoder internal position sensor is messed up. could be the transfercase encoder fork is binding up preventing movement. shorts to the transfercase of the small wires from the fuse block harness.

Thanks again, J cAT. Great advice!

I'm still undecided as to how to approach this whole warranty issue. If the fluid is black, and I change it, will the dealer claim I had maintenance performed without his authorization and thereby void my warranty?

I think I'll just see how the fluid looks. If it's clean, that's great. I can live with that. If it's black, I think I'll phone the dealer immediately and inform him. I don't think any reasonable person would prevent me from changing the fluid in that event.

I think I'll go out and get another Onstar diagnostic right now.

Thanks again!

Bill

Thanks again, J cAT. Great advice!

I'm still undecided as to how to approach this whole warranty issue. If the fluid is black, and I change it, will the dealer claim I had maintenance performed without his authorization and thereby void my warranty?

I think I'll just see how the fluid looks. If it's clean, that's great. I can live with that. If it's black, I think I'll phone the dealer immediately and inform him. I don't think any reasonable person would prevent me from changing the fluid in that event.

I think I'll go out and get another Onstar diagnostic right now.

Thanks again!

Bill

If the fluid is black then I would not change it but return the vehicle to this used car dealer and get my money back. this to rebuild properly will cost 2,ooo.oo......

Sounds like good advice. What if the dealer refuses to take the car back? My only recourse then would be to allow him to service the vehicle. I would lose if I took him to court, if he performs according to the terms of the Warranty.

Of course, these are all "what-ifs". I guess one step at a time. Tomorrow morning I'll know more. Then, it's decision time.

So, Onstar still reports only a code of C0306. They said they have the ability to read multiple codes, and that is the only code showing.

I think in the future, I'll advise anyone looking for a used Tahoe to check the transfer case fluid first!

Sounds like good advice. What if the dealer refuses to take the car back? My only recourse then would be to allow him to service the vehicle. I would lose if I took him to court, if he performs according to the terms of the Warranty.

Of course, these are all "what-ifs". I guess one step at a time. Tomorrow morning I'll know more. Then, it's decision time.

So, Onstar still reports only a code of C0306. They said they have the ability to read multiple codes, and that is the only code showing.

I think in the future, I'll advise anyone looking for a used Tahoe to check the transfer case fluid first!

If you bring back for repair work give a written letter signed , with the defects. then make sure you bring another person as a witness.

have them give you at that time a work order. now you have dates and defects and witnesses.

IN massachusetts many get these issues of defects ,with new vehicles compenstated , when the seller does not repair the defects.
small claims court works quite well.


what happens if they take 2 weeks or longer to repair ? when does the coverage end ? with AAA have it towed down there vehicle OFF. that way mileage zero.

Great points. I wondered that myself. I don't know if AAA will tow it that far. We've been considering upgrading to AAA Premium, which allows for 100 miles.

Great points. I wondered that myself. I don't know if AAA will tow it that far. We've been considering upgrading to AAA Premium, which allows for 100 miles.


I have the AAA premium . I believe it is 100- 120 miles.

If the trac II fluid is black driving to the used car dealer you may get stuck. also just more damage.

Yes, it's 100 miles. There's a three day waiting period.

I didn't think there was the possibility of damage if I left it in 2Hi. But, of course, something's going to be rotating in there. Like maybe the input shaft and the attached parts.

Thanks so much for your advice!

Bill

If the trac II fluid is black driving to the used car dealer you may get stuck. also just more damage.

Well, the fluid's black and has a burnt odor. So I'll call the dealer and see what he says.

So the mechanic plugged in his $7,000 Snap-On diagnostic reader and got the same code as Onstar had read: C0306. He tried the 4WD and it worked! Auto, 2Hi, 4Hi, and 4Lo all working. Of course, the clunking sound when shifting in and out is quite pronounced. Like friggin Loud.
The message cleared itself as well, as well as the DTC. When I got home just now, I had Onstar run a diagnostic, and it came back clear. Go figure. I guess enough shutdown cycles had intervened for the computer to allow another try at shifting.

The mechanic said it would be OK to drive in 2WD.

He also said that all the dealers buy warranties on their cars prior to sale to protect themselves. Whether the end consumer purchases the extended warranty or not, the dealer is covered. If the consumer buys the warranty, so much the better. So, in my case, it won't cost the dealership anything to fix this.

We'll see what the dealer says now.

Greetings to everyone. I have a 2005 tahoe z71 with 39,000 miles. About a year ago i started having trouble with the service 4x4 and stability sys dis. It would rear its ugly head right after using the 4x4, the disappear after awhile. The other day the lights came on again and never went off. Anyway, after reading these posts and found them very helpful, especially the posts from jcat i started my troubleshooting process. I removed the encoder/transfer shift motor and plugged it into my 2003 yukon which also has the nv246 xnsfer case. The problem was duplicated on my yukon which verified the problem. I found on amazon a replacement encoder ac delco part#88962315 for $45. I realized that i could replace just the encoder as the motor worked fine. Here's the iceing on the cake, I disassembled the encoder, cleaned the contacts and re-aligned the brushes and viola! The shift motor works! Reassembled everything and test drive reveals the 4x4 is operating properly. I hope this can help many of you out of a bind. If you dont want to rebuild the motor Doorman has an aftermarket motor for $179.00 on Amazon part #600-910. Many thanks again for everyones input especially jcat. Btw this is my first post here.

Bazinga: That's terrific! You are good!

I agree: j cAT is great! He's been most helpful to me as well.

I have a 2005 silverado 1500 Z-71 with 201,000 miles on it which i have been having a problem with concerning the 4wd. I have found others with sort of the same problem but there are always different details. MY problem is that intermittently, service 4wd will come on the message center and my 4wd buttons will not work. They are still lit, but wont do anything. Other times i will have the same message but the buttons will not be lit. And still other times, the buttons will be lit but the truck will be in 4 LO. I have some mechanical ability so I have started checking things out. I read on one forum that sometimes the soldered connections in the shift button cluster will be bad, so I carefully re-soldered all of those with no result. I have not yet taken it anywhere to get the codes pulled because my dealership wants $200 just to read the codes. I read that 90% of the time it is the encoder ring in the transfer case so I have also removed the shifting mechanism from the transfer case to get a look at the encoder ring. No luck there. I dont know how to "check it" to see if it is good or bad. I am thinking my only avenue is to buy a new encoder ring and replace my old one to see if that is the problem or not but i have read that they need to be "flashed". Would a dealership need to do this? Or is there a way that I can? Any thoughts or suggestions will be greatly appreciated!! If you see that I have done something wrong, please point it out.

For what it's worth: About 2 years ago my 2005 Chevy Tahoe was having the exact symptoms described by "cory e" earlier in this post - warning messages about servicing the 4x4 system which resulted in having the dealer replace the cluster of 4x4 switches in the dash. Problem solved (for a while).
Today (after experiencing the other symptoms that 'cory e' mentions exactly,... stability control and 4x4) my 2005 Chevy Tahoe is going to have its Encoder Motor Sensor changed out at $452.02 (which I assume now is only the part).
Thank you Cory E!

Hey having the same issue as the rest of you, but I replaced the Switch first, everything went well. It switched into 4wd, hi/low, switched out np's, then I drove it a few blocks in 4wd to get the fluids moving. The on-screen code came back on Service 4wd. Now I went to the dealership prior to changing the switch and they told me that these two parts needed to be changed: Encoder Ring and the Switch console itself, Both both parts for $185. After Switch was replaced as I said in the previous sentences, the error came back shortly after. Now I crawled under my Tahoe change the encoder ring, Great tutorial on youtube btw!!!, and then I get the message Se4rvice 4wd, then Stability Control... System Disabled, now I took it back to the dealership and they found 2 more codes after the change that the encoder ring is the issue... I'll get those codes to ya in a few... I also read somewhere else that you cannot move/start the vehicle until you launch the programmer to show that the encoder ring has been changed?? I wasn't going to pay $400+ in labor to fix something that took me less than an hour to do, and I wasn't told that I need to immediately program it neither.

Codes are: c0306,c0321,c0327

I've been having similar issues with my 2006 Yukon. I had originally replaced the Encoder Motor but that didn't solve my problem. I then found a post, that I can't seem to find anymore, that said this problem can also be caused by a loose connection on the cable to the Front Differential. I moved the pins on this plug just slightly so that they would make better contact put the plug back in and wala the problem went away. Well for about a year. Then problem started occurring again. My mechanic read the codes and said it was the Encoder Motor, I don't remember what the code he gave me was. C0327 I think. Anyway, I told him what I had found the time before so he dissembled the plug and cleaned it up but that did not solve the problem this time. I called OnStar to have the read the codes and they say there are not any codes in the system. I'm going to have my mechanic read the codes again and see what he says. Any thoughts? Has anybody else had problems where OnStar couldn't read the codes?

the c0327 is a code that refers to the encoder operation.

could be the motor/wires/fuses/connector/shorted wires/broken wires.

the transfercase fluid should be checked for color and level. bad fluid will cause the encoder to mess up/stick/bind/break internal parts.

transfer case fluid need be blue . if its black have you wallet ready.

Have you ever seen where OnStar diagnostics (GM Goodwrench On Demand Diagnostics) does not show any codes?

Have you ever seen where OnStar diagnostics (GM Goodwrench On Demand Diagnostics) does not show any codes?


if you have service 4wd light on then you have a code with this. possible that GM on star can only retrieve engine codes not drivetrain codes.

if you have service 4wd light on then you have a code with this. possible that GM on star can only retrieve engine codes not drivetrain codes.

Yep, 0327. Going to replace the Encoder Motor first as the one on there has a lifetime warranty and its not really that difficult a job. Next I'll start looking at the wiring harness. Any thoughts on where I could get one specific for the 2006? Because of all the "intermittent" issues I've had with this that is where my guess is the problem really is. I'd like to check continuity on those wires.

Thanks

dbl

Yep, 0327. Going to replace the Encoder Motor first as the one on there has a lifetime warranty and its not really that difficult a job. Next I'll start looking at the wiring harness. Any thoughts on where I could get one specific for the 2006? Because of all the "intermittent" issues I've had with this that is where my guess is the problem really is. I'd like to check continuity on those wires.

Thanks

dbl

what does the transfer case fluid look like ? I change my fluid every 40,000miles. the fluid should be blue. if the fluid is bad the encoder works harder to move. that harness is a tough one to replace. I would inspect for proper routing and that the loom protection material over these wires is in good condition.that the hold downs are being used to secure wires.

these wires are very fragile so go easy on them .

I would not know where you can get them . repairing this would be better . also under the fuse box should be checked for rodents chewing these wires.

Puttin this topic back on the table...1st post on this forum & have read all the replies thus far.

2005 Tahoe Z71 w/110K trouble free miles--
Selector button cluster was not operating & we could not identify whether we were in 2H/Auto4WD/4H/4L.....most often would show us stuck in Auto4WD so we just had it replaced. At the same time recently (just prior to switch replacement) vehicle had difficulty going into gear intermittently. Checked trans fluid, topped it to ensure hot fluid level was correct & it seemed OK but we were still stuck in Auto4WD according to the button cluster (when it decided to light up). Now the new switch/selector works & all driveability is functional except when put in daily driver 2H mode...in which it now pops out of Drive and into Neutral when attempted to operate. Dealer now states we need to remove transfer case for $1047 to disassemble and "see what's wrong". Any educated ideas on this new twist? I've informed the dealer service dept to hold as the truck is there right now. It does operate fine at the moment, but is in Auto4WD....should I drive it outta there & find another opinion based on what I've been told so far? $1000+ to pull the case and disassemble for a "look" seems quite excessive.

Thanks in advance for any advice.
-MOB

**& just talked to them again....failure code was C0327!

with what your saying here you best have them service the transfer case.

IF you take the time to read all that is here on this particular post on this issue you will learn much.

you have a transfer case and it has a special fluid . if the fluid is with 110,000 miles on it I will not be surprised if you will need a complete rebuild.

I would also take the time to read the owners manual as well.

the code is the encoder motor. that gets damaged from low/worn fluid.

you need to crawl under the vehicle to check it.

all drive train fluids require replacing every 40,000 miles.

Thanks for the reply....

having read through not only this forum, but others very similar as well.....the issues have been very similar with the resulting problems being related to the encoder motor and/or sensor and/or electrical connections causing operational failures. What I find strange is that they're not even mentioning any these items as potential causes & are jumping right to yanking out & disassembling the transfer case with a hefty price to do it.

Thanks for the reply....

having read through not only this forum, but others very similar as well.....the issues have been very similar with the resulting problems being related to the encoder motor and/or sensor and/or electrical connections causing operational failures. What I find strange is that they're not even mentioning any these items as potential causes & are jumping right to yanking out & disassembling the transfer case with a hefty price to do it.

some of those people don't know much about this . the encoder is damaged from old fluid . the encoder is a motor and when the motor cannot move easy it gets burned out. it will also blow a fuse 20AMP on some called the ATC . other modules its called something else.

replacing all drive train fluids means front and rear diff / transfercase and the transmission pan drop clean replace filter if dirty.

the rear diff you remove cover after the drain and clean out the gear box of the metal debris dust sludge..

those that know how to do this encoder , it can be done for 200.00 ..dealership will charge 800.00 or so for the encoder replacing, but you could have more than that , because if the internals are broken you will get this code as well.. black colored fluid usually means a re-build..

Ok so here's my non-mechanic dumb dumb question.... How do I check the transfer case fluid for levels & coloration? I'm presuming there's no dipstick for that. I think I'm going to pick up the car & evaluate my options before authorizing any further ($1000++) services at the dealer service dept....

Ok so here's my non-mechanic dumb dumb question.... How do I check the transfer case fluid for levels & coloration? I'm presuming there's no dipstick for that. I think I'm going to pick up the car & evaluate my options before authorizing any further ($1000++) services at the dealer service dept....

under the vehicle in the middle is the transfer case . it has a big shaft connected to it that goes to the rear diff. On the bottom you will see a drain plug. up above that a few inches you will see the fill plug. you unscrew the top plug I think it is 15 MM. then you stick a plastic tie rap/ty strap into the hole. it should be a blue oil and just below the hole on level ground. if some pours out no big deal. I fill to the top of the hole and put the plug back on . torque to about 15 ft lbs. same as a spark plug... never over tighten because the case can crack. if the oil is black then you will need have a shop check it out or you can have the fluid replaced and see if it still works properly.

so what did they say was wrong ? you ask about the fluid ???

I believe this 2005 uses the GM trac II fluid in this transfer case. the NNBS 2007 -14 , GM I believed changed it to the dexron VI.

when ever changing the fluids in these always check with the GM dealership using your vin # to ensure you use/or the repair shop puts in the correct fluid. and yes there are idiot repair / lube shops that will put in the wrong fluid.

Thanks for the reply....

having read through not only this forum, but others very similar as well.....the issues have been very similar with the resulting problems being related to the encoder motor and/or sensor and/or electrical connections causing operational failures. What I find strange is that they're not even mentioning any these items as potential causes & are jumping right to yanking out & disassembling the transfer case with a hefty price to do it.

SO MOB916 how much did they screw you out of , to fix it ?

what did they replace ?