4wheel drive will not engage, encoder?

Tiny
MDCHEETHAM
  • MEMBER
  • 2002 CHEVROLET SILVERADO
  • 130,000 MILES
4wheel drive will not engage. Dash indicator light indicates it is engaged. I suspect actuator or x-fer case motor. Is there any way to determine/test which one it is? I lost the 4 wheel drive going about 35 MPH in 4HI in a snowstorm. I appreciate any info you can give me. I don't want to just start replacing parts. Thank You
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Thursday, February 14th, 2013 AT 9:23 PM

44 Replies

Tiny
JACOBANDNICKOLAS
  • EXPERT
I always check to see if there is power to the actuator. If there is, then the actuator is most likely bad. If there is no power, then you need to check the relay, switch. To see where power is lost.
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Friday, February 15th, 2013 AT 3:43 AM
Tiny
DBKS
  • MEMBER
  • 2002 CHEVROLET SILVERADO
  • V8
  • 4WD
  • AUTOMATIC
  • 160,000 MILES
Dose'nt switch from 2 wheel to 4 wheel, diagnosed at GM 4x4 controler still the same, no binding at selecter on tranfercase/ no power to encoder, need wireing diagram
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Tuesday, May 26th, 2020 AT 6:17 PM (Merged)
Tiny
HMAC300
  • EXPERT
Check to make sure you are gettingpower at the axle. :If they are saying it's the encoder motor it very well may be. here is the diagram.........


https://www.2carpros.com/forum/automotive_pictures/406719_2002_chev_4wd_1.jpg

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Tuesday, May 26th, 2020 AT 6:17 PM (Merged)
Tiny
GUNNER1982
  • MEMBER
  • 2000 CHEVROLET SILVERADO
  • V8
  • 4WD
  • AUTOMATIC
  • 218,000 MILES
My truck blows the ATC fuse as soon as you put it in. I unhooked the Transfer case motor and the fuse did not blow. Hooked it back up and blam blew. Ran a scan. With c0323 low voltage or smthn and a g1038 not sure what that one is. Do I need to replace the transfer case shift motor? Or the dash selector switch? Or look 4 smthn else?
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Tuesday, May 26th, 2020 AT 6:17 PM (Merged)
Tiny
JACK42
  • EXPERT
They had more problems with the transfer case motor than the switches. If you unplugged the motor and all was good, I would start there, motors are much more likely to short than a switch, at least enough to blow fuses
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Tuesday, May 26th, 2020 AT 6:17 PM (Merged)
Tiny
GUNNER1982
  • MEMBER
Replaced Transfer case motor, stopped blowing the atc fuse, but now it will not come out of 4hi. Pull atc fuse and the front actuator will disengage the front, put it back in an the acuator engages the front. When you push the 2hi actuator and motor sound like there trying to engage but light blinks and goes back to 4hi. Removed Transfer case motor and could shift transfer case manually. Did I get a bad transfer case motor or is there something else to look for?
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Tuesday, May 26th, 2020 AT 6:17 PM (Merged)
Tiny
JACK42
  • EXPERT
You may have gotten a bad one. They also had some problems with the front actuator, but I dont think that would make it stay in 4wd. Check the switch too, when the motor was shorted, it could have hurt it with too much amperage draw
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Tuesday, May 26th, 2020 AT 6:17 PM (Merged)
Tiny
GUNNER1982
  • MEMBER
Put on another new TCM and a switch. Will shift from 4hi to 4lo to auto but still no 2high. Im trying to get a wiring diagram to look for some grounds maybe. Im puzzled.
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Tuesday, May 26th, 2020 AT 6:17 PM (Merged)
Tiny
JACK42
  • EXPERT
These had issue with the encoder motor causing this,

The wiring diagrams and instructions to change the encoder motor are attached below
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Tuesday, May 26th, 2020 AT 6:17 PM (Merged)
Tiny
GUNNER1982
  • MEMBER
Back again. Still stuck in 4hi. The control module behind the selctor switch in the dash. Do you know the part number or is it called anything besides control module and where can I buy one?
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Tuesday, May 26th, 2020 AT 6:17 PM (Merged)
Tiny
JACK42
  • EXPERT
Automatic transfer case control module is what it is called. It is located behind the dash left side above headlight switch. Have you had it scanned to see if it is the problem? A trans shop should be able to do that
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Tuesday, May 26th, 2020 AT 6:17 PM (Merged)
Tiny
GUNNER1982
  • MEMBER
Yes we have scanned it and the dtc is c0323 the transfer case lock circuit low. I used the manual from the site u gave me and went through the ten step process it advised for that code and the only step we havn't done is replace that module. As step 9 recomends. How costly is this module and can I get it online? Any idea of part number? Are talking about a scan or a flash something gm has to do?
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Tuesday, May 26th, 2020 AT 6:17 PM (Merged)
Tiny
JACK42
  • EXPERT
Looks like it may be around $350. Mitchell doesnt say anyhting about programming it. Probably doesnt need it, it is an off on kind of part not like a PCM. Should be plug-n-play
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Tuesday, May 26th, 2020 AT 6:17 PM (Merged)
Tiny
GREG CASTELLO
  • MEMBER
Hi, my 99 Suburban also blows transfer case fuse. Unplugging the 4 wire plug on the transfer case prevents fuse from blowing. I can leave 2 wire plug in TC and plug in front differential in place. Does this mean transfer case motor or less likely bad wire in harness?
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Tuesday, May 26th, 2020 AT 6:17 PM (Merged)
Tiny
KEN
  • ADMIN
9 times out of 10 it is the encoder motor that needs to be changed here are diagrams below to help you with the repair. Check out the diagrams (below). Please let us know what happens.
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Tuesday, May 26th, 2020 AT 6:17 PM (Merged)
Tiny
GREG CASTELLO
  • MEMBER
Ken, the motor worked like a charm I plugged it in before taking down the old one and no blown fuse, confirming it wasn't a wiring harness issue causing short. Other than figuring out the stupid clamp on the rear boot, and how to get the boot off, it was a piece of cake. Easily less than an hour job. Fortunately the female on the motor was in the same position as the male shaft on the TC, I'm not sure how I would have gotten them to line up otherwise. Power the motor or spin the rear wheels?
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Tuesday, May 26th, 2020 AT 6:17 PM (Merged)
Tiny
KEN
  • ADMIN
Yep either would have worked, glad you got it fixed. Use 2CarPros anytime, we are here to help. Please tell a friend.
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Tuesday, May 26th, 2020 AT 6:17 PM (Merged)
Tiny
GEORGE HUGHES
  • MEMBER
  • 2001 CHEVROLET SILVERADO
  • V8
  • 4WD
  • AUTOMATIC
  • 194,500 MILES
I lost my 4WD. I tried to engage the 4WD by pushing the buttons on the 4WD switch. The lights on the switch would not light and the veh would not change from 2WD to 4WD. The service 4WD light came on in the instrument panel. I removed the battery cable to see if it would reset the code, the service 4WD lightwent out but there still appeares to be no power to the switch. I have replaced the actuator and the 4WD switch but I still appear to have no power to the switch. As stated above I can not engage the 4WD. Do you have any idea of the problem. Thanks
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Tuesday, May 26th, 2020 AT 6:18 PM (Merged)
Tiny
PEAR69
  • MEMBER
Turn the key to run and go to the front axle actuator, located on the front differential. Unplug it and test the brown wire for 12 volts. This is the same circuit as the 4wd switch. If there is no voltage then you probably have a blown fuse -- I believe it is fuse number 24 under the dash - 25amp.
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Tuesday, May 26th, 2020 AT 6:18 PM (Merged)
Tiny
MATTPINKIERT
  • MEMBER
  • 2001 CHEVROLET SILVERADO
  • V8
  • 4WD
  • AUTOMATIC
  • 130,000 MILES
Hi. I have a z71 silverado with autotrac 4wd. I was driving in 4 hi when the trucked skidded to a halt. In 2wd the truck drives great. When I try to use 4wd, any auto hi or low the front wheels are locked up and the rear will do a burnout. Any ideas on what might be happening? I'm suspecting the encoder motor on the transfer case. Thanks
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Tuesday, May 26th, 2020 AT 6:18 PM (Merged)

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