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!)