I am the original owner of a 2004 4x4 Silverado Extended Cab Z71 which has 107k miles on it. My dad is borrowing the truck and just called me with a problem. While towing in 2 wheel drive, the "2 wheel drive" light at the 2wd button went off (no selections are lit) and the message flashed on the dash "service 4 wheel drive". Truck will not go into 4 wheel drive when you hit the button, but is running fine is 2wd. Truck is well maintained and have never had any trouble before. Wondering if there is something common that goes wrong? If I plug into the computer with an obd2 scanner and read any codes that might be there, will that help figure it out? Any advice as to the best way to avoid a trip to the shop will be appreciated, though I see it coming anyway.
There are 1000 threads on this, which is why you are getting no replies.
Check the fuse? Fuse ok, If all the lights are out, it's the switch, common failure.
I will do a search. Thank you for the reply. Yes, all lights are out, but fuse not checked. I hope a search provides what switch needs to be swapped. Thanks again :)
my guess is that your 4wd switch is going, I have the same problem on my truck. it works occassionally, but the lights have a tendency to not work
How do I open the panel to replace the switch? Is the switch right behind the 2wd/4wd buttons?
Last edited by GrandNational; 01-30-2011 at 04:23 PM.
The switch is the actual buttons
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its possibly the switch. you need to have the tccm scanned . sound more like the module is dead. sometimes a reprogram will "wake" it up. codes in the module will tell if its the switch or module.
I guess I am confused. I thought there was one switch, but are you saying that there is a switch for each of the 4 buttons? I am also assuming that I can't read the codes for the transmission with a regular obd2 scanner. Correct?
Its a single switch unit that has all of the buttons on it. I dont know that a regular OBD2 scanner will read
04 ECSB 5.3 4x4 Z71
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05+ front brake swap, Suburban rear brake swap,Rusty door bottoms,Line X,PCM4Less tune
with the mileage on it. It is probably the encoder motor on the transfer case. I have gone thru 2 of them in 2 yrs.
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It's either the Dash switch or the encoder motor. I actually replaced the sensor inside the encoder motor and it took care of the issues.
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In the life of the truck's 107k miles, 4wd has barely ever been used, so the buttons and the mechanism haven't been used much either. Is changing the sensor in the encoder motor a big job? Heck is pulling the encoder motor a big job? I am experienced with motors, trannys and transfer cases I am not. If I end up buying a new encoder motor, is the sensor in the encoder motor included?
Last edited by GrandNational; 01-31-2011 at 07:48 AM.
The encoder motor isn't cheap, and swapping it may not resolve the issue.
If you have a service 4wd message, I woudl have the dealer diagnose, then replace the parts myself as neccessary, as randomly replacing parts that could still be serviceable will get expensive.
There are quite a few threads here on the issue, and swappign switch panels is quite often the solution, that being said, there is still the potential for it to be an encoder motor issue, a module issue, or a wiring harness issue.
Well, my best guess at this point is that it's the module, let's see if you all will agree. I had told my dad to check the fuse, then hit the dash at the switch and if neither of those worked, to disconnect the battery for 30 seconds. He got to the disconnect the battery step and it worked, everything is working fine again. I had stopped at the dealer and got a new switch just in case that was it (the truck was stuck in the snow in a rural spot and couldn't be moved without 4wd). So am I right that it's probably the module given the battery disconnect worked? I can't see how it would would be fixed the way it was if it was the switch or the encoder motor. But then, I am no expert :)
Last edited by GrandNational; 01-31-2011 at 04:28 PM.
Anyone agree with me? Or am I wrong?
My thought is that a broken circuit or short wouldn't be fixed by a power down, it would still be there. But a power down would reboot electronics/computer.