Stuck in 4WD

[wsteele]

Fless and Fuvar0715 thank you for your replies. Fless are you saying the issue is in the encoder motor assembly? I am confused with the order of operation so I am getting hung up on if the issue is with the encoder motor, the transfer case control module, or the selector switch. If you’re feeling is that it’s the motor assembly then I will go with your educated guess and I appreciate you sharing the knowledge. Fubar0715 I am located in just west of Boston. Not sure how to add that into my profile but I will look into it. Thanks again for all of the info and if anyone else has anything to add, please post. Thanks again.

You don’t have enough information to make a definitive judgement on which of the three candidate components (wiring, TC motor, TCCM) might be the culprit. If the wiring is OK, then the GM engineers who wrote the shop manual think the TC motor is next most likely.

If you want to be sure which component will fix the problem, you need to follow the diagnostics outlined above.

Most of the harness likely is not the problem, but the short leg that goes to the motor itself is under the chassis and routed pretty close to the FW drive shaft, so might could get chafed/cut.

The next candidate in the test protocol is in your the TC Motor. If neither the wiring or the TC Motor are bad, then the book says it is the TCCM.

As Fless pointed out, you can do the test steps above to get an exact determination, shotgun parts replacement or take it to a competent shop that does a lot of GM LT work and they will get it fixed in a few hours or less.

I think if there are no obvious issues with the portion of the harness going to the motor, a shotgun approach of first installing a replacement TC Motor and if that doesn’t fix it replace the TCCM, probably would yield a successful result. The problem with that approach is you don’t have a scan tool that can do the motor relearn (which might not be a big deal if you get the motor and TC in synch and the state the TCCM thinks things are in, are compatible).

If you buy a new TC motor and TCCM, again, you may need the motor relearn and it would be really nice to have the calibrations appropriate for your VIN flashed into your TCCM.

All that points to it being a good idea to take it to a qualified shop, or maybe using the extra money you will pay a shop for their equipment and know how and buy your own Tech 2 and maybe a DMM.

 

[Fless]

Fless and Fuvar0715 thank you for your replies. Fless are you saying the issue is in the encoder motor assembly? I am confused with the order of operation so I am getting hung up on if the issue is with the encoder motor, the transfer case control module, or the selector switch. If you’re feeling is that it’s the motor assembly then I will go with your educated guess and I appreciate you sharing the knowledge. Fubar0715 I am located in just west of Boston. Not sure how to add that into my profile but I will look into it. Thanks again for all of the info and if anyone else has anything to add, please post. Thanks again.

Agree with @wsteele. A better scanner might indicate the failure type byte which is in addition to the code; that may narrow things down. Without it, though, the diag steps shown first show the test for signals coming from the Transfer Case Control Module (TCCM). The component test specs the required resistance of the actuator (sometimes called the TC encoder motor).

So without testing those items it's difficult to tell which device is causing the issue. If I were you, I'd see if another scanner would narrow it down, or seek additional help. It's most likely that the actuator, as a mechanical device, has worn parts. You could throw a new actuator on the TC ($200) I don't think it requires programming), but be prepared for a TCCM replacement, which may require programming. Some of the older TCCMs are available rebuilt from Dorman that don't require it, but I'm not familiar enough with your year to know. Check RockAuto for parts, or the GM store in Amazon. There could also be a wiring problem, which is what the diag steps would confirm.

Hope that helps. Let us know what you decide to do.

 

[Fless]

As a further commment, I guess there is a possibility that the switch is bad, but I don't think the lock circuit code points to that. If you can find one relatively inexpensive, maybe in a junkyard, you might change it out. But, again, I would concentrate my efforts elsewhere, at least initially.

 

[UpAndDown]

Click on your Forum name in the top right corner of your screen if you are on a computer. Scroll down, fill in the info, click save, done.

Done. Thank you

 

[UpAndDown]

There are 2 of us in the NE area that have Tech2 devices...both of us are very green in the use but we have one. Both us are in Southern New Hampshire.

Thanks for that info Fubar0715. I think I’m going to take a shot at the TC encoder motor.

 

[UpAndDown]

wsteele and Fless thanks very much for the replies. I think I am going to throw a TC encoder motor on it in the next week or so and see if that’s it. I know it’s a shot in the dark. Does anyone know for sure if the encoder motor needs a relearn procedure done on it for sure or not as wsteele mentioned? I have read that the TCCM requires it, but if you buy a Dorman unit it does a self calibration. The encoder motor however, I have not read about a procedure being needed. If it is needed, will this render the truck undrivable until it is completed? Any and all replies are welcomed and appreciated. Thanks again for all of the help.

 

[wsteele]

wsteele and Fless thanks very much for the replies. I think I am going to throw a TC encoder motor on it in the next week or so and see if that’s it. I know it’s a shot in the dark. Does anyone know for sure if the encoder motor needs a relearn procedure done on it for sure or not as wsteele mentioned? I have read that the TCCM requires it, but if you buy a Dorman unit it does a self calibration. The encoder motor however, I have not read about a procedure being needed. If it is needed, will this render the truck undrivable until it is completed? Any and all replies are welcomed and appreciated. Thanks again for all of the help.

The shop manual calls out a relearn procedure with the scan tool when the motor or tccm is replaced.

I have read service articles that state if you put the TC in neutral before the exchange, it will be synchronized as the new motor will come in Neutral, hence neither device will be out of synch (there is no intelligence in the motor itself). I have read other stuff that says you can just manually turn the TC selector to neutral with a pair of vice grips after removing the old motor and they will be ready to go, but if it were me, I would be concerned the TCCM would think it was in the last position it knew and be out of synch with where the motor and TC were positioned after assembly.

If I couldn’t be sure I got the TC to the neutral position electronically (that is the TCCM thought it was in neutral), at a minimum I would leave the battery disconnected overnight before hooking it up and trying to fire things up. Definitely unhook the battery before starting the replacement of the motor.

 

[wsteele]

Sitting here with a cup of coffee and my other MY specific repair book (not factory shop manual), there is no mention of the relearn procedure. They just say to manually set the shift position to neutral after removing the old motor so the new motor is aligned with the shift shaft. After install, it is implied the TCCM will read the position from the encoder ring that it is in neutral and that is what will be indicated on the switch.

Inthink if I could get it to go into neutral electronically, I would do that before jacking the truck up, but if it won’t change to neutral from 4WH, I wouldn’t worry about it, I would just put it in neutral manually underneath.

 

[swathdiver]

Can the OP not see my posts and the troubleshooting guide? If so, he's wasting time.

 

[Fless]

@swathdiver it's a personal choice to bypass the diag. Not necessarily recommended but it happens all the time. You can lead a horse to water....

@UpAndDown When you're ready to start the work, look at your owner's manual for the specific procedure to put the transfer case into neutral, and at least try that before disconnecting the battery. Be sure to chock a wheel both in front and back of it, since the tranny parking pawl won't have any effect on keeping the truck from rolling.

 

[swathdiver]

wsteele and Fless thanks very much for the replies. I think I am going to throw a TC encoder motor on it in the next week or so and see if that’s it. I know it’s a shot in the dark. Does anyone know for sure if the encoder motor needs a relearn procedure done on it for sure or not as wsteele mentioned? I have read that the TCCM requires it, but if you buy a Dorman unit it does a self calibration. The encoder motor however, I have not read about a procedure being needed. If it is needed, will this render the truck undrivable until it is completed? Any and all replies are welcomed and appreciated. Thanks again for all of the help.

Were you able to see all of post #2 including the photo with the procedure for diagnosis?

 

[UpAndDown]

Were you able to see all of post #2 including the photo with the procedure for diagnosis?

I was. Thank you for posting it. A lot of it is somewhat confusing to me though. I am going to take the foolish approach and shotgun the TC encoder motor assembly and see where that gets me. At worst, I will have a new part, which seems to be prone to failure anyways.

 

[UpAndDown]

Thanks again guys for all of the help. Reading up online has shown some people say a relearn is needed with the TCCM replacement, while others have said that holding the dial switch over in the N position for about 30 seconds will allow a relearn on the TCCM. As far as a relearn on the TC encoder motor itself, I haven’t seen anything other that what was posted here a few posts back from wsteele. If I can’t get the truck to go into N electrically before I swap the motor out, which way do I turn the sprocket or shaft, whatever is sticking out of the TC, and how do I know when I have reached the N position? Perhaps I should start a new thread specifically on the replacement of the TC encoder motor as it would probably catch people’s eyes that have done that swap where this one may not. Once again I am beyond appreciative for all of the help and information provided so far.

 

[wsteele]

I was. Thank you for posting it. A lot of it is somewhat confusing to me though. I am going to take the foolish approach and shotgun the TC encoder motor assembly and see where that gets me. At worst, I will have a new part, which seems to be prone to failure anyways.

If you are feeling particularly lucky (or just like options versus equity), it is possible to just replace the encoder (the position sensor), which is the part that most frequently fails, in the part that most frequently fails.

On the motor learn process, as best as I can tell from the sparse information I have found (google isn't as good as it used to be), it is about dialing tolerances. That is, getting the motor in the center of any tolerance build ups between the motor and the TC. I think if you can't get it to go into neutral before you start, simply turning the shaft so it is in neutral and installing the new motor will get you back on the road just fine (if it was the motor in the first place). Everything I have seen is the TCCM senses the motor position and displays that in the switch when power is applied.

As long as you get the new motor installed, it appears the old TCCM will see the position of the motor sensor and display it on the switch and that will also indicate the TC switch status as they are synched mechanically (which should be neutral as that is where the new motor will be set up).

If it doesn't display it when everything is installed, you know you didn't;t have a motor/encoder problem.

As far as what the shop manual indicates with regard to the relearn, refer to James' post #2. It calls for a relearn for either components replacement.

 

[Fless]

The TC probably has three positions -- just guessing -- so if you have no joy getting it into neutral electronically, for neutral turn the TC shaft (the one that the encoder motor would) to a setting so that the rear propshaft spins freely. You may have to rotate the propshaft slightly to be able to turn the small shift shaft, thereby taking tension off of the TC. First, though, if the encoder manufacturer specifies that the motor is shipped in the neutral position, all the better. You can match the position of the TC's keyed shaft with the motor position. That's probably the only way you'll get it mounted anyway.

I think if both the TC and the encoder motor are in the same mode (neutral, preferably, but I wouldn't turn the encoder motor while it's not mounted) then the TCCM is going to know that by what the encoder motor reports. It's a simple matter of the unique resistance of the motor's internal position sensor getting reported to the TCCM for the TCCM to figure out the mode, if that makes sense.

 

[Fless]

My responses have been based on earlier TC motors; however, yours doesn't connect the same way physically as I thought; it's a somewhat different interface. I'm not sure about all the talk about having to have it in neutral, etc. There's not a shaft on the TC, from what I can see. You'll need to do some further research on if the TC needs to be in neutral or if the motor does some kind of auto-sense.

 

[UpAndDown]

Fless and wsteele thank you both once again. Fless I see what you’re saying. There doesn’t appear to be a keyway on the pictures I’ve seen so the transfer case and the encoder motor appear to be able to be mated in any position. Hopefully the functional encoder will then tell the TCCM what position it is in. Am I off base here? Still may start another encoder motor replacement specific thread as there has to be a bunch of guys here who have swapped it out. As always, comments and suggestions are appreciated and welcomed.

 

[wsteele]

My responses have been based on earlier TC motors; however, yours doesn't connect the same way physically as I thought; it's a somewhat different interface. I'm not sure about all the talk about having to have it in neutral, etc. There's not a shaft on the TC, from what I can see. You'll need to do some further research on if the TC needs to be in neutral or if the motor does some kind of auto-sense.

View attachment 349113

I agree, I was looking at 07 parts (my model year) but it appears the 08’s are different.

Another approach to get the motor and TC synched, would be to connect the motor before bolting it down. Apply power and your switch will likely display neutral (or whatever the encoder says it is to the TCCM). Then select 4H on the switch (assuming you never got it in neutral before starting). This will position the motor to where your TC was before the old motor was removed and likely you will be synched.

With all those teeth, I can kind if see why learn might be needed.

 

[wsteele]

Found this video. No mention of having it in neutral before motor replacement. In the video, it looks like the position sensor might be a separate piece next to it.

 

[Fless]

I would recommend getting a subscription to AlldataDIY for your truck. Then you'll have access to all sorts of good info.

I saw that video too; strange that there's no mention of indexing or a learn procedure, if one is needed.