4X4 light flashes five times will not shift into four wheel drive

Tiny
94 TRANSAM
  • MECHANIC
  • 1996 CHEVROLET TAHOE
  • 5.7L
  • V8
  • 4WD
  • AUTOMATIC
  • 308,000 MILES
I had the truck in 4H, needed more torque so I hit the 4L button and all was well. Got unstuck in the snow and hit the 2H button and it went right into 2H. A few miles down the road I hit some more snow so I went to hit the 4H button again and both the 4H and 4L buttons flashed five times and went back to 2H. Now it doesn't matter which button I hit (4H or 4L) both lights flash five times and go out. No shift noise at all and intermittently all the buttons go dead, no lights for a few minutes like an auto reset breaker pops and it takes a few to reset.

I am familiar with this system and have fixed many but I have never seen both lights flash at once.

Anyone heard of this?
Sunday, February 24th, 2019 AT 6:36 PM

7 Replies

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 47,643 POSTS
Hello,

Yes this happens when the encoder goes on on the transfer case. Here are diagrams to help you change the unit out. #73 is what you need to replace. Check out the diagrams (below). Please let us know what happens.
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Tuesday, February 26th, 2019 AT 11:26 AM
Tiny
94 TRANSAM
  • MECHANIC
  • 680 POSTS
Hi Ken, Thanks for the reply. So the back story is I plowed through a four foot snowbank into a driveway when I did the truck kicked to the right and the rear tire slid into a ditch with five feet of snow in it. The relevance here is the whole drive train was hot and all that snow packed tight under the truck in every single nook. Even all the way up over the transmission. With it all being hot the snow melted enough to soak the rest of the snow which in turn quickly froze solid.
So I got under there yesterday to check for ripped wires etc and found a solid block of ice from the rear of the oil pan back to the start of the driveshaft. Couldn't see the transmission, front drive shaft or transfer case at all. So chiseling away and melting with map gas I got to the front drive shaft which wouldn't turn at all. Long story long I got all the ice out and it shifted right in to 4H and 4L right away. I'm not sure what exactly was wrong except maybe the front shaft has to be able to turn a bit to align the transfer gears. Or maybe the encoder was mad at me and said no way I don't know but it is one for the books. Thank you have a good one.
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Tuesday, February 26th, 2019 AT 8:19 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 47,643 POSTS
That.S a good one I think you were right about the encoder. Use 2CarPros anytime, we are here to help. Please tell a friend.
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Wednesday, February 27th, 2019 AT 10:42 AM
Tiny
JNIENHAUS1
  • MEMBER
  • 1 POST
  • 1999 CHEVROLET TAHOE
1999 Chevy Tahoe

I have a 1999 Tahoe, with dash push button 2H, auto, 4H and 4L buttons. The check 4wd light came on a couple weeks ago and the tech checked the code and said it was a switch problem. I took a 100 mi trip yesterday and after stopping to unload it had shifted to 4L and stayed there. The dash switch was replaced and now their telling me the tranfer case decoder is bad< $800.00. I cannot find this part or any info online any where. Tell me all you know
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Wednesday, February 27th, 2019 AT 10:42 AM (Merged)
Tiny
RHALL77
  • MECHANIC
  • 3,361 POSTS
I think you mean a encoder motor. Ihave them double check it, there is a sensor inside it that goes bad often and can cause the same thing
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Wednesday, February 27th, 2019 AT 10:42 AM (Merged)
Tiny
DAVIDC23
  • MEMBER
  • 1 POST
  • 1999 CHEVROLET TAHOE
  • V8
  • 4WD
  • AUTOMATIC
  • 104,000 MILES
Sometimes I'll drive the truck and it works fine, but then I put it on park and when I proceed to drive it again, the truck won't move and makes a loud screeching noise when I try to put it back on park. The service 4WD light is idle. It won't reverse or drive. The only way I can get it to run again is by pressing the 2WD button while putting it in neutral. I was told the what is causing this problem are the 4WD sensors. I've replaced them and it still keeps having the same problem. What do you think could be causing this?
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Wednesday, February 27th, 2019 AT 10:42 AM (Merged)
Tiny
BMRFIXIT
  • MECHANIC
  • 19,053 POSTS
Need to have it scanned for codes
I would suspect the motor actuator on the transfer case (Encoder)

need manual CHECK IT @
https://www.2carpros.com/kpages/auto_repair_manuals.htm
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Wednesday, February 27th, 2019 AT 10:42 AM (Merged)

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