4wd Service - Stuck In 4wd

[Terry2001]

4WD Service – Stuck in 4WD

 

I have been involved in a similar thread (http://www.gm-trucks.com/forums/index.php?...rt=#entry815696) with a similar problem. I am posting a new thread to get feedback from people that have encountered the "Service 4WD" message and could also NOT dis-engage the truck from 4WD. As most of the posts I see have the message but cannot get the truck to switch into 4WD.

 

If you have had both the "4WD Service" message and your truck has been stuck in 4WD what has fixed it? Dash Switch? Actuator Motor on Transfer Case? Actuator Motor Sensor ONLY? TCCM (Transfer Case Control Module, behind dash) replacement or re-flash? Or any combination of these?

 

 

In my case I have eliminated the Dash switch as suspect and all fuses/connections. This leaves me with finding which component to try next. I am leaning towards the TCCM because:

 

First thought…….I can "make" the truck switch out of 4wd (using procedure below) which tells me that the Actuator motor is functioning. Not sure how the Actuator Sensor plays into this theory however.

 

Second thought……..Also on a working truck when you hit the button to switch between 4HI and 2HI (or any other) you hear a clicking sound similar to a solenoid/relay coming from the area of the TCCM, I do not hear this in mine indicating possible failure?

 

Final thought………. (another theory) something is telling the truck to go into and stay in 4WD, I can make it come out (procedure below) but if the ATC fuse from the engine compartment is not removed it goes back in as soon as I start to drive again. So the only things that tell the truck to go into 4WD is by hitting the button/switch (which I am not) which sends a message to the TCCM to send power to the Actuator. My theory is that the TCCM is failing and is sending that message to the Actuator without being asked?

 

 

I have

- "Service 4WD" on shortly after every startup, stays on.

- Stuck in 4HI,

- NO lights on dash switch indicating 2HI, 4Lo, etc...(except all flash momentarily on startup, typ.)

- Pushing switch buttons does not appear to affect anything (no sounds of trying to engage/dis-engage)

- no real action to cause problem, just driving paved side street 4WD came on, switch lights went out and then noticed in 4WD by feel of the drive.

 

Checked fuses in the dash panel and under the hood, all were good.

 

Checked for loose wiring, appeared/felt fine.

 

Swapped out the switch for a known working, no change.

 

DID NOT have the codes read at the dealer. I may if I cannot get any further but have read many that are given codes that indicate (for example) replace Actuator Motor, which they do only to have to also replace the TCCM afterwards because it was not the Actuator.

 

 

To disengage the 4x4 without going under the truck I did the following (thoughts others may benefit from this procedure):

 

1. Remove the negative cable from the battery; wait a few minutes (3 minutes worked for me).

2. Reconnect the negative (ground) cable to the battery.

3. Start the truck only (do not put it in gear, do not hit any buttons, etc...)

4. While the truck is running remove the "ATC" fuse from the fuse panel in the engine compartment.

(Not a pro so this may or may not be an advisable technique!!!)

5. Test drive to ensure 2wd. Still working for me after 2 days of driving and troubleshooting.

 

 

 

 

 

Any tips for me based on your problem/solution would be appreciated? Anything added will hopefully help my problem and aid others trying to troubleshoot this problem.

 

2001 GMC Sierra 1500

 

Thanks,

 

Terry

[seadoons]

Any one reading this post should read the link to the thread Terry posted above - it will give background and my story as to what happened to my truck recently.

 

Terry - the dealer will probably charge you $100 to read the codes and tell you what the problem is. This will allow you to at least narrow down what the problem is. My dealer was even kind enough to give me his thoughts and was even willing to tell me how to do the repair myself. Based on all of your descriptions above - I am going with the TCCM.

 

One thing I didn't mention was that I am not sure my dealer ever tried to re-program my old TCCM. I think they are just used to throwing parts at vehicles since warranty is usually paying for it. Oh well.

[tenntoby]

I think your gonna have to have it scanned for codes to go any further with diag.This will point in the right direction on where to go next.Does your truck have the auto 4x4 option(np8)?Common problems are the selector switch, encoder sensor, and in some cases clutch plate failure and tccm failure(module locks up and stores c0550).hth

[Terry2001]

I think your gonna have to have it scanned for codes to go any further with diag.This will point in the right direction on where to go next.Does your truck have the auto 4x4 option(np8)?Common problems are the selector switch, encoder sensor, and in some cases clutch plate failure and tccm failure(module locks up and stores c0550).hth

 

 

It has the Auto 4x4 option. Confirmed the "selector switch" is operational.

 

You mention it could be the TCCM, that it locks up. Is there a way for it to be serviced or is replacement required?

 

 

Thanks for the info,

Terry

[dwhults]

I have a 99 OBS Yukon but had the same problem as you. It ended up being the TCCM. $350 later and it was good. I got code C0315 - Motor Ground Circuit Open. My service manual's check procedure led me to the TCCM. If you do need a new TCCM, change it yourself. The dealer wanted $250 for install. All I needed was some patience and cursing and I was good to go. Tight spot but not worth $250 for labor. Oh and I have the Auto 4x4 (NP8).

 

If you have access to a Scanner (Actron) it can scan your TCCM codes. Go to Autozone or somewhere to get it scanned.

[seadoons]

I spoke with the folks at O'Reilly and they said that they could not read transmission codes. That doesn't mean that you shouldn't at least have them try - they do it for free. My code was c0324 - something about a circuit being open (maybe a high circuit). Don't quote me on that.

 

Regarding the TCCM - I ended up paying the dealer to do it b/c my truck was stuck in 4WD and I didn't really have time to do it myself as I needed the truck the next day. The main reason that I had them do it was once they installed the new module they still had to use their programmers to get it to work correctly. If I had installed it myself I still would have ended up at the dealership - and they would have charged me an additional hour of labor to program it on top of the hour that I had already paid for for them to scan the original problem. I think they charged me three hours of labor plus the cost of the part...$886 out the door. OUCH.

[Terry2001]

I think your gonna have to have it scanned for codes to go any further with diag.This will point in the right direction on where to go next.Does your truck have the auto 4x4 option(np8)?Common problems are the selector switch, encoder sensor, and in some cases clutch plate failure and tccm failure(module locks up and stores c0550).hth

 

 

 

I have finally made time to have the codes scanned. It showed a C0327 only. I disconnected the wiring connector from the Encoder/Actuator and I still receive the "Service 4WD". Also it is a NP8 transfer case (Auto 4x4). Any thoughts?

 

 

Thanks,

Terry

[Terry2001]

4WD Service – Stuck in 4WD

 

I have been involved in a similar thread (http://www.gm-trucks.com/forums/index.php?...rt=#entry815696) with a similar problem. I am posting a new thread to get feedback from people that have encountered the "Service 4WD" message and could also NOT dis-engage the truck from 4WD. As most of the posts I see have the message but cannot get the truck to switch into 4WD.

 

If you have had both the "4WD Service" message and your truck has been stuck in 4WD what has fixed it? Dash Switch? Actuator Motor on Transfer Case? Actuator Motor Sensor ONLY? TCCM (Transfer Case Control Module, behind dash) replacement or re-flash? Or any combination of these?

 

 

In my case I have eliminated the Dash switch as suspect and all fuses/connections. This leaves me with finding which component to try next. I am leaning towards the TCCM because:

 

First thought…….I can "make" the truck switch out of 4wd (using procedure below) which tells me that the Actuator motor is functioning. Not sure how the Actuator Sensor plays into this theory however.

 

Second thought……..Also on a working truck when you hit the button to switch between 4HI and 2HI (or any other) you hear a clicking sound similar to a solenoid/relay coming from the area of the TCCM, I do not hear this in mine indicating possible failure?

 

Final thought………. (another theory) something is telling the truck to go into and stay in 4WD, I can make it come out (procedure below) but if the ATC fuse from the engine compartment is not removed it goes back in as soon as I start to drive again. So the only things that tell the truck to go into 4WD is by hitting the button/switch (which I am not) which sends a message to the TCCM to send power to the Actuator. My theory is that the TCCM is failing and is sending that message to the Actuator without being asked?

 

 

I have

- "Service 4WD" on shortly after every startup, stays on.

- Stuck in 4HI,

- NO lights on dash switch indicating 2HI, 4Lo, etc...(except all flash momentarily on startup, typ.)

- Pushing switch buttons does not appear to affect anything (no sounds of trying to engage/dis-engage)

- no real action to cause problem, just driving paved side street 4WD came on, switch lights went out and then noticed in 4WD by feel of the drive.

 

Checked fuses in the dash panel and under the hood, all were good.

 

Checked for loose wiring, appeared/felt fine.

 

Swapped out the switch for a known working, no change.

 

DID NOT have the codes read at the dealer. I may if I cannot get any further but have read many that are given codes that indicate (for example) replace Actuator Motor, which they do only to have to also replace the TCCM afterwards because it was not the Actuator.

 

 

To disengage the 4x4 without going under the truck I did the following (thoughts others may benefit from this procedure):

 

1. Remove the negative cable from the battery; wait a few minutes (3 minutes worked for me).

2. Reconnect the negative (ground) cable to the battery.

3. Start the truck only (do not put it in gear, do not hit any buttons, etc...)

4. While the truck is running remove the "ATC" fuse from the fuse panel in the engine compartment.

(Not a pro so this may or may not be an advisable technique!!!)

5. Test drive to ensure 2wd. Still working for me after 2 days of driving and troubleshooting.

 

 

 

 

 

Any tips for me based on your problem/solution would be appreciated? Anything added will hopefully help my problem and aid others trying to troubleshoot this problem.

 

2001 GMC Sierra 1500

 

Thanks,

 

Terry

 

 

 

So to re-cap.....the scan showed DTC C0327. Now I'm stuck in 4 Low, actually it's 2 Low by using the method above I can stop it from locking in the front diff (so no tire binding/chirping while taking turns on asphalt). Any suggestions on how to get the transfer case to switch to the 2Hi/4Hi position from 4Low?

 

 

Thanks.

[Terry2001]

4WD Service – Stuck in 4WD

 

I have been involved in a similar thread (http://www.gm-trucks.com/forums/index.php?...rt=#entry815696) with a similar problem. I am posting a new thread to get feedback from people that have encountered the "Service 4WD" message and could also NOT dis-engage the truck from 4WD. As most of the posts I see have the message but cannot get the truck to switch into 4WD.

 

If you have had both the "4WD Service" message and your truck has been stuck in 4WD what has fixed it? Dash Switch? Actuator Motor on Transfer Case? Actuator Motor Sensor ONLY? TCCM (Transfer Case Control Module, behind dash) replacement or re-flash? Or any combination of these?

 

 

In my case I have eliminated the Dash switch as suspect and all fuses/connections. This leaves me with finding which component to try next. I am leaning towards the TCCM because:

 

First thought…….I can "make" the truck switch out of 4wd (using procedure below) which tells me that the Actuator motor is functioning. Not sure how the Actuator Sensor plays into this theory however.

 

Second thought……..Also on a working truck when you hit the button to switch between 4HI and 2HI (or any other) you hear a clicking sound similar to a solenoid/relay coming from the area of the TCCM, I do not hear this in mine indicating possible failure?

 

Final thought………. (another theory) something is telling the truck to go into and stay in 4WD, I can make it come out (procedure below) but if the ATC fuse from the engine compartment is not removed it goes back in as soon as I start to drive again. So the only things that tell the truck to go into 4WD is by hitting the button/switch (which I am not) which sends a message to the TCCM to send power to the Actuator. My theory is that the TCCM is failing and is sending that message to the Actuator without being asked?

 

 

I have

- "Service 4WD" on shortly after every startup, stays on.

- Stuck in 4HI,

- NO lights on dash switch indicating 2HI, 4Lo, etc...(except all flash momentarily on startup, typ.)

- Pushing switch buttons does not appear to affect anything (no sounds of trying to engage/dis-engage)

- no real action to cause problem, just driving paved side street 4WD came on, switch lights went out and then noticed in 4WD by feel of the drive.

 

Checked fuses in the dash panel and under the hood, all were good.

 

Checked for loose wiring, appeared/felt fine.

 

Swapped out the switch for a known working, no change.

 

DID NOT have the codes read at the dealer. I may if I cannot get any further but have read many that are given codes that indicate (for example) replace Actuator Motor, which they do only to have to also replace the TCCM afterwards because it was not the Actuator.

 

 

To disengage the 4x4 without going under the truck I did the following (thoughts others may benefit from this procedure):

 

1. Remove the negative cable from the battery; wait a few minutes (3 minutes worked for me).

2. Reconnect the negative (ground) cable to the battery.

3. Start the truck only (do not put it in gear, do not hit any buttons, etc...)

4. While the truck is running remove the "ATC" fuse from the fuse panel in the engine compartment.

(Not a pro so this may or may not be an advisable technique!!!)

5. Test drive to ensure 2wd. Still working for me after 2 days of driving and troubleshooting.

 

 

 

 

 

Any tips for me based on your problem/solution would be appreciated? Anything added will hopefully help my problem and aid others trying to troubleshoot this problem.

 

2001 GMC Sierra 1500

 

Thanks,

 

Terry

 

 

 

So to re-cap.....the scan showed DTC C0327. Now I'm stuck in 4 Low, actually it's 2 Low by using the method above I can stop it from locking in the front diff (so no tire binding/chirping while taking turns on asphalt). Any suggestions on how to get the transfer case to switch to the 2Hi/4Hi position from 4Low?

 

 

Thanks.

 

 

 

Now I have it out of 4LO by disconnecting the neg. terminal from the battery, once re-connected and before the transfer case module sends a trouble code (and locks up tight) I managed to hit the switch while rolling in neutral and made it back to 4Hi!!!

 

Based on code and diagnostics it looks like a TCCM, just ordered a used one. Just for reference, here in Canada they want $914.00 + express shipping if I'm in a rush!!!!! The used ones are $125.00, worth a try for the price difference as it is very easy to physically install and test. Now I just need to know if a used unit from a 2001 Yukon, same engine and t-case will need to be re-programmed at dealer?

 

 

Thanks. Will post this T-Case module re-program question as a new post as it has moved away from the title of the initial post. Will keep posting here as hopefully it will help someone in the future to have all this together.

[Terry2001]

Replaced TCCM (Used) Update. Scroll to the bottom to see latest entry.

 

 

 

4WD Service – Stuck in 4WD

 

I have been involved in a similar thread (http://www.gm-trucks.com/forums/index.php?...rt=#entry815696) with a similar problem. I am posting a new thread to get feedback from people that have encountered the "Service 4WD" message and could also NOT dis-engage the truck from 4WD. As most of the posts I see have the message but cannot get the truck to switch into 4WD.

 

If you have had both the "4WD Service" message and your truck has been stuck in 4WD what has fixed it? Dash Switch? Actuator Motor on Transfer Case? Actuator Motor Sensor ONLY? TCCM (Transfer Case Control Module, behind dash) replacement or re-flash? Or any combination of these?

 

 

In my case I have eliminated the Dash switch as suspect and all fuses/connections. This leaves me with finding which component to try next. I am leaning towards the TCCM because:

 

First thought…….I can "make" the truck switch out of 4wd (using procedure below) which tells me that the Actuator motor is functioning. Not sure how the Actuator Sensor plays into this theory however.

 

Second thought……..Also on a working truck when you hit the button to switch between 4HI and 2HI (or any other) you hear a clicking sound similar to a solenoid/relay coming from the area of the TCCM, I do not hear this in mine indicating possible failure?

 

Final thought………. (another theory) something is telling the truck to go into and stay in 4WD, I can make it come out (procedure below) but if the ATC fuse from the engine compartment is not removed it goes back in as soon as I start to drive again. So the only things that tell the truck to go into 4WD is by hitting the button/switch (which I am not) which sends a message to the TCCM to send power to the Actuator. My theory is that the TCCM is failing and is sending that message to the Actuator without being asked?

 

 

I have

- "Service 4WD" on shortly after every startup, stays on.

- Stuck in 4HI,

- NO lights on dash switch indicating 2HI, 4Lo, etc...(except all flash momentarily on startup, typ.)

- Pushing switch buttons does not appear to affect anything (no sounds of trying to engage/dis-engage)

- no real action to cause problem, just driving paved side street 4WD came on, switch lights went out and then noticed in 4WD by feel of the drive.

 

Checked fuses in the dash panel and under the hood, all were good.

 

Checked for loose wiring, appeared/felt fine.

 

Swapped out the switch for a known working, no change.

 

DID NOT have the codes read at the dealer. I may if I cannot get any further but have read many that are given codes that indicate (for example) replace Actuator Motor, which they do only to have to also replace the TCCM afterwards because it was not the Actuator.

 

 

To disengage the 4x4 without going under the truck I did the following (thoughts others may benefit from this procedure):

 

1. Remove the negative cable from the battery; wait a few minutes (3 minutes worked for me).

2. Reconnect the negative (ground) cable to the battery.

3. Start the truck only (do not put it in gear, do not hit any buttons, etc...)

4. While the truck is running remove the "ATC" fuse from the fuse panel in the engine compartment.

(Not a pro so this may or may not be an advisable technique!!!)

5. Test drive to ensure 2wd. Still working for me after 2 days of driving and troubleshooting.

 

 

 

 

 

Any tips for me based on your problem/solution would be appreciated? Anything added will hopefully help my problem and aid others trying to troubleshoot this problem.

 

2001 GMC Sierra 1500

 

Thanks,

 

Terry

 

 

 

 

---DTC C0327/Stuck in 4LO now----------------------------------------------------------

 

 

So to re-cap.....the scan showed DTC C0327. Now I'm stuck in 4 Low, actually it's 2 Low by using the method above I can stop it from locking in the front diff (so no tire binding/chirping while taking turns on asphalt). Any suggestions on how to get the transfer case to switch to the 2Hi/4Hi position from 4Low?

 

 

Thanks.

 

 

 

 

---Out of 4LO/Order Used TCCM/Re-programm?--------------------------------------------

 

Now I have it out of 4LO by disconnecting the neg. terminal from the battery, once re-connected and before the transfer case module sends a trouble code (and locks up tight) I managed to hit the switch while rolling in neutral and made it back to 4Hi!!!

 

Based on code and diagnostics it looks like a TCCM, just ordered a used one. Just for reference, here in Canada they want $914.00 + express shipping if I'm in a rush!!!!! The used ones are $125.00, worth a try for the price difference as it is very easy to physically install and test. Now I just need to know if a used unit from a 2001 Yukon, same engine and t-case will need to be re-programmed at dealer?

 

 

Thanks. Will post this T-Case module re-program question as a new post as it has moved away from the title of the initial post. Will keep posting here as hopefully it will help someone in the future to have all this together.

 

 

 

 

---Replaced TCCM (Used) Update---------------------------------------------------------

 

I received my used TCCM from the junkyard and installed today. The problem was not fix but it has changed things.

 

1. Remove negative battery cable.

 

2. Remove old TCCM and install used TCCM (not re-programmed, should I?).

 

 

 

3. Re-connected negative battery cable.

 

4. Start truck, appears the lights are now flashing more consistently. Still "Service 4WD" and cannot switch.

 

5. Re-installed the original TCCM and low and behold all was normal on startup. The switch lite up properly, I was able to switch between 2HI and Auto with no problems. This continued to work even during a test drive. It did fail however once I attempted to switch to 4HI or 4LO, once failed I would get the "Service 4WD" message and the switch would stop functioning completely. After ignition off/on the switch would show no lights. NOTE: once the 4HI/4LO button was depressed I could hear the transfer case (Encoder Motor) attempting to switch maybe twice then stop and light up the "Service 4WD", it is attempting to switch just not able to complete.

 

6. Install the used (junkyard) TCCM again and it showed same as point 4.

 

7. Re-installed the original TCCM (point 5.) and all was the same as step 5.

 

An AllData diagnostic tree for DTC C0327 pointed me to the TCCM based on the fact that the "Service 4WD" would light up as soon as the key was turned on (maybe 10 seconds) even if the wiring harness was disconnected from the Encoder Motor (also some other testing for proper voltage at different pins and good continuity). Now that the "Service 4WD" waits until I hit the 4HI/4LO buttons it APPEARS to indicate the Encoder Motor or Sensor??

 

 

 

Any input is appreciated, constructive criticisms also welcomed.

 

Thanks,

Terry

 

 

 

 

---To be continued!-----------------------------------------------------------------------------------