Service 4wd - but only in 2wd

[SnowDrifter]

Finally bothering me enough to deal with this

I'll generally get a service 4wd popup after about 30 mins of driving. But only if I'm in 4wd. If I'm in 4hi / 4auto, message never shows up. Furthermore, if I go from 4wd to 2wd while driving, the message will appear after several minutes.

- 4hi/4 auto works as intended and I have verified it does send power to the front wheels.

- And 2wd successfully disconnects the front drive shaft and can be spun by hand.

- The 4wd selection switch has been replaced

- The 4wd selection switch has been verified good with a multimeter

- My bluetooth code scanner detects no codes with torque pro (unknown if it's the OBDLink MX or Torque not detecting it, or if there are no codes thrown)



What are my next steps here?

 

[wjburken]

Check your fluid level.

My 2004 Silverado had the similar symptoms and it ended up being due to the common issue they had with a pin wearing a hole in the housing. As I was taking it in to get looked at, my transfer case turned into a box of gravel and I was barely able to get into the service bay.

It could definitely be other things, but I’d for sure check your fluid level.

 

[SnowDrifter]

Check your fluid level.

My 2004 Silverado had the similar symptoms and it ended up being due to the common issue they had with a pin wearing a hole in the housing. As I was taking it in to get looked at, my transfer case turned into a box of gravel and I was barely able to get into the service bay.

It could definitely be other things, but I’d for sure check your fluid level.

Let me crawl under there real quick

 

[S33k3r]

There are 5 pieces to the push button 4WD system. The button (you have already tested), the Transfer Case Control Module, the (encoder) motor than translates electric signals into physical motion, the transfer case itself, and the wiring in between everything. What you are describing, to me, seems like an encoder motor issue, based on the information you have provided. If you had the pin hole in the transfer case, I'm thinking you would be hearing something, and more than just 2WD would have an issue. If it is the encoder motor,it could be stuck in auto or 4HI, and that is what is causing the message.

 

[SnowDrifter]

Let me crawl under there real quick

Fluid level, condition are good

 

[SnowDrifter]

There are 5 pieces to the push button 4WD system. The button (you have already tested), the Transfer Case Control Module, the (encoder) motor than translates electric signals into physical motion, the transfer case itself, and the wiring in between everything. What you are describing, to me, seems like an encoder motor issue, based on the information you have provided. If you had the pin hole in the transfer case, I'm thinking you would be hearing something, and more than just 2WD would have an issue. If it is the encoder motor,it could be stuck in auto or 4HI, and that is what is causing the message.

Maybe encoder has a dead spot on it? Wiper worn or something?

It goes in and out of 4wd just fine. Was able to validate that

 

[S33k3r]

Maybe encoder has a dead spot on it? Wiper worn or something?

It goes in and out of 4wd just fine. Was able to validate that

The TCCM rarely goes out, but it can. Best bet is if you have someone with a similar vehicle nearby, and swap them out. But my money is still on the encoder motor. It's a little expensive to fire out the parts cannon though, so you might want to troubleshoot a little more.

 

[SnowDrifter]

Pulled a C0327 code

time to go digging

Anyone in the Seattle area happen to have a tech2 I could borrow for the day?

 

[Sam Harris]

When mine was acting like this (almost 3 years, since I had bought the truck), it was the encoder motor ring. This is a cheap part, and pretty easy to replace. I believe it is: 88962315, and is about $22 on Amazon. I had the same kind of flaky behavior from mine and it would often go to “Service 4WD” any time I actually used it. This replacement has resolved the issue. I do believe I had the same code from the Tech2, but unfortunately I can’t find my notes on that one… after looking up your C0327 code, I’m fairly confident that’s also what I had. Sorry I can’t say 100%, but pretty confident and it’s a cheap, fairly easy fix.

 

[SnowDrifter]

When mine was acting like this (almost 3 years, since I had bought the truck), it was the encoder motor ring. This is a cheap part, and pretty easy to replace. I believe it is: 88962315, and is about $22 on Amazon. I had the same kind of flaky behavior from mine and it would often go to “Service 4WD” any time I actually used it. This replacement has resolved the issue. I do believe I had the same code from the Tech2, but unfortunately I can’t find my notes on that one… after looking up your C0327 code, I’m fairly confident that’s also what I had. Sorry I can’t say 100%, but pretty confident and it’s a cheap, fairly easy fix.

Here's the diagnostic tree

Yeah, I could shotgun a part at it. 20 bucks isn't a big deal. but I really, really hate guessing. Cause even at 20 bucks, if I'm wrong, now that pushes cost of repair up plus I just wasted my time.

tech2 would get me there in about 5 minutes. Realistically, I think you're right though. Given that it only throws the code in 2wd, and NEVER in any of the others. Which would indicate that step 4 is true by proxy, indicating encoder sensor.

As of right now, it looks like there are 3 major endpoints for the diagnostic tree

1. Wiring / water intrusion to harness

2. Encoder sensor, like you said

3. TCCM (Hope not!)

 

[Fless]

Like you said, it's best to get a Tech 2 or other capable scanner on it, especially to verify the trouble code that's setting the message.

I know what mine was doing was not what you're experiencing, but mine had symptoms of being in Auto when I'd switch it to 4HI, that 1/2 second or so lag while the front diff actuator engaged. The 4HI mode light on the switch would light, 4HI was commanded (per the Tech 2), but the actual mode was Auto (again, shown in the Tech 2 at the same time). It had no codes. Turned out to be the encoder motor, like @Sam Harris.

 

[SnowDrifter]

Like you said, it's best to get a Tech 2 or other capable scanner on it, especially to verify the trouble code that's setting the message.

I know what mine was doing was not what you're experiencing, but mine had symptoms of being in Auto when I'd switch it to 4HI, that 1/2 second or so lag while the front diff actuator engaged. The 4HI mode light on the switch would light, 4HI was commanded (per the Tech 2), but the actual mode was Auto (again, shown in the Tech 2 at the same time). It had no codes. Turned out to be the encoder motor, like @Sam Harris.

Well

I guess now:

1. how much a tech 2 costs (I'm seeing a wide spread from 100-500)

2. where to get one that isn't a horrid knockoff and actually works (concerns from above)

3. Cost / feature differential between tech 2 and a much more general purpose shop scanner. I'm open to suggestions on this one

3a. Google poke is nonconclusive for... anything. Harbor freight's Zurich makes me sus, house brand stuff. Unclear if it requires the subscription to function, or if it's only for 'up to date' info. Autel's website doesn't have any comparison tool I could find. And what I could locate on google gives redundant info (if they all work, why the price difference?) Snap-on / matco / etc are immediate price-out

3b. Would want to stay in the <600 range, with no need for subscriptions for diagnostic / 2way comm use. Could stretch to 800 if there's a *really* strong proposition, but not a dollar more.

3c. Would want good and proper 2 way communication. Actuation of various bits and bobs / calibration(abs bleed, actuators, BMS learning, keyfob, TCCM relearn, etc). Also comprehensive live data - relavent to current thread. Concern is advertising vs. fuctionality. I don't care about seeing data from O2 sensors. I want proper positional / actual time / whatever the hell else data. Anything less than that - it's an expensive code-reader and not worth the cost to me.

3d. Oscope, current clamp, etc functionality would be great to have, but not worth a thousand bucks if that's what it costs.

3e. Used is just fine!

 

[George B]

I will just put this here:

Tech 2 Purchase

Time to buy a Tech 2 ..I see a ton of threads when I do a search units clones vs. originals ETC... Where is the best place to purchase? Are there accessories I should be looking at in addition to the unit? Is it even possible to buy a non-clone unit? TIA

www.tahoeyukonforum.com

 

[Fless]

In addition to the thread @George B posted, if you haven't yet read this 3-page thread, it might clarify a few things for you.

Migration from ACDelco TDS to GM Techline Connect for Tech 2 Users

Hi Folks, As you probably know, ACDelco TDS (TIS2Win) site for Service Programming Software (SPS) has been retired, effective September, and current subscription holders need to migrate to its replacement GM Techline Connect. Below, I offer you the process that I used to perform this...

www.tahoeyukonforum.com

Chinacardiags (I think I have that spelled correctly) seems to be a good place to buy a Tech 2; it's where I got mine. You can get them with/without a case for prices between $270 and about $350. You can program (free) your NBS modules with the TIS2000 software included as long as you use a WinXP computer or a Virtual Machine running XP. But that takes a bit of persistence to accomplish; not impossible, but will take some research. Personally I have an old XP laptop that I've dedicated to this instead of the VM path. Otherwise you can pay the VIN fee for Techline and do it online using Win10 as noted in several of the posts on that thread.

Others here will have more recommendations, I'm sure.

 

[Udaman21]

I had this happen a few times. Always happened after it rained or went thru a puddle. Took off the shift motor and torn it down. Found water in the unit. Seals failed. Bought a new sensor and sealed the unit with RTV. Problem solved.

 

[V327839]

I forgot the codes I pulled when something similar happened to me. I replaced the encoder ring easily and cheaply. That fixed the main issue. A later issue is with the speed sensors. They detect the moment of the front and rear driveshafts. They are also cheap and there are two on the tcase. They are identical and just screw in. Might look into those as well. I have a bad front sensor which won’t let me shift OUT of 4hi, but worked fine during the last snow storm for now. Go figure.

 

[2591tdj]

Search this forum for the topic “Service 4WD”. There are a number of discussions and solutions to this all too common problem. Mine was also due to the encoder ring which is an easy and inexpensive replacement.

 

[06 Taco]

I had a similar problem on my 06 Tahoe Z71. Check the grounds that are under the driver side B pillar. Check all the plugs and connections on the transfer case shifter motor and the front axle solenoid. I believe that there are threads on this site that will give you the proper resistance readings for the different pins. There is definitely info on you tube.

 

[SnowDrifter]

Well

Grounds / connections all looked OK. Pulled them off, sanded down, dielectric grease, and some water proofing on top. Removed the plugs and noted no corrosion in the pins. No change.

Ordered the sensor ring based on a best educated guess. I really should get a proper scanner..... But every time I look at the price, I just think to myself: Ok but do I really *need* it.

Will update the thread later with outcomes.

 

[S33k3r]

Well

Grounds / connections all looked OK. Pulled them off, sanded down, dielectric grease, and some water proofing on top. Removed the plugs and noted no corrosion in the pins. No change.

Ordered the sensor ring based on a best educated guess. I really should get a proper scanner..... But every time I look at the price, I just think to myself: Ok but do I really *need* it.

Will update the thread later with outcomes.

What price are you seeing? I finally buckled down and got one after 4 years... I'd suggest against waiting that long.