2005 Suburban service 4wd message truck is in 2 wd

[TJ Baker]

I have a series of pictures taken during the job. The biggest annoyance to me was having to remove the front driveshaft to get the shift motor unit out. Most folks replace the whole unit. I would only recommend replacing the sensor by itself if you have both the time and patience for the job AND you know the rest of the shift motor is sound. It would truly suck to do all this and then discover it was not the real problem. I verified my sensor trouble with a tech 2 but it can also be checked out with a DMM and the schematics.

The primary trouble with these is a degradation of the resistive materials of the sensor by many hours of vibrations where the metal pickups ride in the 2wd position. Here's a look at mine where I have opened up the sensor. (I enjoy seeing how things actually work)

 

[Sstevieboy0208]

I have a series of pictures taken during the job. The biggest annoyance to me was having to remove the front driveshaft to get the shift motor unit out. Most folks replace the whole unit. I would only recommend replacing the sensor by itself if you have both the time and patience for the job AND you know the rest of the shift motor is sound. It would truly suck to do all this and then discover it was not the real problem. I verified my sensor trouble with a tech 2 but it can also be checked out with a DMM and the schematics.

The primary trouble with these is a degradation of the resistive materials of the sensor by many hours of vibrations where the metal pickups ride in the 2wd position. Here's a look at mine where I have opened up the sensor. (I enjoy seeing how things actually work). The resistive material has been wiped clean in this picture but I left the buildup of crud on the pickup.View attachment 248194 View attachment 248195

The result of this is a fluctuating return voltage signal which prevents the TCCM from determining the current position of the Transfer Case Shift Motor.

View attachment 248196

I truly appreciate all the help and in all honesty I'm not in a hurry to get it done so I might just take some time doing more digging definitely will need it done before the winter as I live in Ohio. Got a few other issues that I should take care of. I just bought it as I used to have one identical and missed it. Got a hell of a deal on so can't complain much and all that needs done i can do it myself.

 

[swathdiver]

So the results are in and I have a code C0321. Most searches says encoder motor sensor

Transfer Case Lock Circuit. if you got the symptom number with the code it will tell you if it was a short to battery, ground, circuit open or bad signal.

 

[Sstevieboy0208]

Transfer Case Lock Circuit. if you got the symptom number with the code it will tell you if it was a short to battery, ground, circuit open or bad signal.

All it says was the code and transfer case lock circuit fault

 

[TJ Baker]

transfer case lock circuit fault

As Swathdiver aptly pointed out the C0321 is the lock circuit. Nothing to do with the encoder sensor which is usually a code C0327. I have not experienced troubles in that with my vehicles. As I understand it the lock circuit is to be energizedt release the motor as a shift is underway. At least that is how I think it works, perhaps someone with specific knowledge here can chime in. Either way, a DMM and a good knowledge of how to test electrical circuits is your friend here. These days everyone says you must have the codes!! Before the days of codes and such,,,, things still got diagnosed and repaired!!!

 

[Fless]

All it says was the code and transfer case lock circuit fault

I'm not sure if it relates specifically to your code, but one easy thing to do is to remove and clean the two ground connections that are under the driver's side body, right behind the LF wheel. Look underneath the body there. There should be two bolts, with one or two wires each. Don't just look at them, remove the bolts, clean the body contact and the terminals, and reconnect. Then paint or otherwise protect those grounds.

EDIT: in this video it's the first set of grounds that he points out:

 

[Sstevieboy0208]

I'm not sure if it relates specifically to your code, but one easy thing to do is to remove and clean the two ground connections that are under the driver's side body, right behind the LF wheel. Look underneath the body there. There should be two bolts, with one or two wires each. Don't just look at them, remove the bolts, clean the body contact and the terminals, and reconnect. Then paint or otherwise protect those grounds.

EDIT: in this video it's the first set of grounds that he points out:

Thank you for the video. I will try that as soon as the rain stops. Worth a shot before I start diving deeper into the issue. Thank you

 

[Fless]

Know that one of those grounds can affect the 4x4 functions. Don't ask me how I know. LOL

 

[Sstevieboy0208]

Know that one of those grounds can affect the 4x4 functions. Don't ask me how I know. LOL

I will check into it and post updates. Thank you very much