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Has anyone ever have a "SERVICE 4WD" message come up on the dash? Nothing seems to be wrong with it...it drives the same when the message is up as it does when it isnt. this is a intermittent problem. it doesnt come on sometimes and sometimes it does. one day i noticed it while i was driving and the red neutral light was on, i am guess that means a problem, but when i stopped and shut it off and got back in and started it it never happened again. just dont know if it is a computer problem or what?? can anyone help?
 

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DMAX LML
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i used to have that problem on my 03 1500...just like you described...would come on every few months once then shut it off and next start up it would be back to normal. never looked into it though
 

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From what I understand it is a pretty common problem and is related to the selection switch showing signs of going bad.
 

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My sister had a 1999 1500 Silverado and her's came on once. Took it to the dealer under warranty and they replaced the 4 button selector switch. Took care of it.
 

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Subscribed have the same problem.
 

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I have seen and replaced many switches in my days as a service tech at GMC dealer. For exactly the reasons described. Another common problem was the position sensor inside the encoder motor (T-case shift motor). Scan TCCM for codes if any. That will lead to the fix. What year is your truck?
 

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I had it come on one time when I had to start the truck when it had not been plugged in on a cold night. went away after like 2 secconds and never came back again.
 

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I have the same issue now. I just had new injectors put in and when I got it back I noticed the "service 4wd" light on. I thought maybe a vacuum line or somthing didnt get put back on, now im wondering if its the switch. drives fine, goes in and out of 4wd fine. just the service 4wd light comes on. it hasnt come on for 3 days, then it came on today.
 

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i used to have that problem on my 03 1500...just like you described...would come on every few months once then shut it off and next start up it would be back to normal. never looked into it though
same here, been that way for years. I use 4x4 several times a week, never had an issue. :rockin
 

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I am having the "Service 4WD" problem now. The code it throws is C0327 which indicates a problem with the Encoder Motor Sensor (also called Range Position Sensor). The part costs $100 at the stealer and you have to remove the Encoder motor from the Transfer Case to replace the sensor.

Here is a video showing how to replace the sensor:


The Actuator motor costs $692.72 from the dealer and that would fix it if you just want to swap the part in. Replacing the actual failed part in the Actuator takes a little more work plus you have to get a reflash of the computer program. I've found that the truck is drivable after the sensor replacement though, so I'll take it to my local shop to reflash. My local mechanic recommends getting GM parts (GM Parts Direct has the whole Actuator for $402.75) so I may go that way, depending on answers. The sensor from GM Parts Direct was about $50 so that's what I bought

The sensor replacement looks pretty easy and would save me a lot.

The Stealer service mgr told me horror stories of the transfer case switching to 4 LO while driving, locking up all 4 wheels. Not sure that's accurate though since they have their agenda going.

Update: Getting the Actuator out of my truck was a hassle. Not a lot of space to get that last bolt out. I was trying to avoid removing the drive-shaft and ended up having to remove the front u-joint and the rear boot clamp and sliding the shaft forward to clear that bolt. My truck has a bracket under the t-case that is in the way of easily removing the Actuator like the video shows. I had to twist it around a bit and it eventually came out without removing that bracket. The replacement of the sensor was pretty much like the video showed. I'll update this after I finish installing the thing as I'm sure I'll have more fun stuff to impart.

Final update: The sensor replacement didn't work. Still unable to get it out of 4WD-Low. Bit the bullet and got a new Actuator motor from the local dealer for $600 & change. Since I know how to do this swap now, it was easy. Fired up the truck and it shifts great now. Note that I didn't replace the switch block for this fix because that wasn't the code it was throwing. I also did not need to get the computer reset for this to work. Once you remove the actuator motor and have a new replacement in hand, make sure the new one matches what is on the transfer case or it won't go in. The solution was to raise the rear wheels off the ground and turn the driveshaft so I could line up the two parts. The above video speaks to this alignment problem but not the solution.
 

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if the code is a C0327 just swap the encoder motor yourself. They are pretty easy. Open first beer, drop the front drive shaft, pull the bolts off holding the motor on, manually shift the tcase into neutral, throw the new motor on, reinstall the driveshaft, finish last beer. No programming necessary and it wont switch to 4lo and lock the wheels up.

Sent from my DROIDX
 

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if the code is a C0327 just swap the encoder motor yourself. They are pretty easy. Open first beer, drop the front drive shaft, pull the bolts off holding the motor on, manually shift the tcase into neutral, throw the new motor on, reinstall the driveshaft, finish last beer. No programming necessary and it wont switch to 4lo and lock the wheels up.

Sent from my DROIDX
$400 for the new Encoder motor vs. $100 for a sensor and a bunch more work. Hmmm!
 

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I fixed a Tahoe a while back that had the same switch issue. Turns out there was a common issue with a solder joint on the terminals on the back. I removed theswitch, took apart the case and resoldered the terminals.
 

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If the code thrown is C0327, the problem as stated in the TSB, is with the sensor in the Actuator. That part is about $50 (p/n # 88962315) from GMPartsDirect.com vs. $400 for the actuator from them. As the video shows, the replacement of the sensor isn't difficult and that is the route I chose. The Dealer Parts person kept insisting I needed the Actuator ($692 from them) until he asked the service mgr who told him that if the code was C0327, the part to replace is the sensor, not the Actuator. Maybe the Parts guy gets a commission?
 

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I fixed a Tahoe a while back that had the same switch issue. Turns out there was a common issue with a solder joint on the terminals on the back. I removed theswitch, took apart the case and resoldered the terminals.
Did the samething for a friend and it has been fine since.
 

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Just had mine checked and its the interior 4wd selector switch. Easy fix = good news !
 
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