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Discussion Starter · #1 ·
2003 Siverado 2500HD with Duramax.

Haven't used 4x4 in a couple of weeks and it's been months since trying to use 4x4 low (and it worked great then). Last evening I went to use 4x4 and was surprised to see the light on for 4x4 low. Several attempts to get it to go to 4x4 high or low didn't work. Tried it in neutral and in drive while doing really slow. Also tried it in drive when at a stop. Light blinks for a long time and then stops blinking, solid light stay on 4x4 low.

So..I don't think the button was pushed to get it to 4x4 low..I'm thinking some failure somewhere has this indication showing up.

Code showing on my tablet is P0836.

Luckily I also have a 2005 2500HD duramax. I confirmed with dealership that part number for the push button is the same and for the encoder motor. 19259312 for the push button and 19125856 for the encoder.

Is next reasonable step to swap the push buttons or is there something else simple that I am missing/should try?

When I turn the truck tightly on pavement it doesn't seem like it is in 4x4 and some indications on my tablet when looking at "live data" seem to show it's not in 4x4.

On my tablet the "encoder gear position" seems to flash back and forth between "neutral" and "2wd", even though the push button on the truck seems to be stuck in 4x4 low.

Thoughts?


Best,

NH


Above video shows encoder in "neutral".


Above video shows in 2wd.
 

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Probably your encoder in the stepper motor, I had to replace mine on a 2003 suburban. The if the encoder shows one setting but the computer thinks it's another, that will happen.
 

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Discussion Starter · #3 ·
Is this the part you are talking about?


Any ideas on troubleshooting ahead of time? I hope to swap 4x4 push buttons tomorrow to at least rule that out.

Thanks for the reply.

Best

NH
 

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No I'm talking about the encoder ring, inside the part you posted.



There is a way to test the encoder circuit before you replace it. I found it on you tube, but it was for a different problem, the trouble shooting steps were the same.

If you go this route, you will also need a new gasket. The old one will probably not fit back in.

And I wouldn't use a dorman made in China replacement part. But that's just me.

I couldn't find the video quickly but this might help.


Here it gives you the resistance value of each switch.

The other time I had trouble was when the transfer case had the pump rub problem and all the fluid evaporated out. Luckily it was still under warranty for that.
 

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Do not try to put power to encoder motor if it's not installed in vehicle as it can turn too far and mess up internal timing.

Luckily there are timing marks on the gears inside encoder motor, if you drop one out. Read up on instructions for new motor, and adjust your shifter to the position a new one will be shipped as. You can shift the transfer case with a pair of channel locks. We had to remove one of the driveshafts to get the stepper motor out. You may not need to but it makes it easier. I'm going from memory and it was a couple years ago.

You can pull the connector on the motor and read the voltage being sent down to encoder motor. But you will need to clear codes every time you push a button. The push button switch module is just a board with different resistors for each button. The tccm sends a signal, I forget if it's 5 or 12 volts to the switch panel, the reads what voltage it gets back. Then sends a signal to the encoder to see if it's the same as the switch. If it is, then it turns on the light solid. If it's not it can do many things like lighting up the wrong switch, constantly flashing a light, or turn all lights off.
 

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Discussion Starter · #7 ·
Well...I think I got lucky on this one. Turned out to be just a bad switch. I took the switch out of my 2005 to test this one and it worked perfectly. So bought a new switch for 2005 and called it a day.

NH
 

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Well...I think I got lucky on this one. Turned out to be just a bad switch. I took the switch out of my 2005 to test this one and it worked perfectly. So bought a new switch for 2005 and called it a day.

NH
Glad you have the issue resolved.
Thanks for giving us an update!

Merry Christmas to you and family!
(y)
 

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Discussion Starter · #9 ·
And Merry Christmas to you your family as well. I really appreciate this forum..helps me organize my approach to repair and upgrades...so I can minimize the "parts canon" method. :)

I've got a bunch of fund duramax projects I'm hoping to do this coming year. Will try to document them here with photos an updates.

My 6.5s have been parked for a bit...hope to get those running good and might sell one or both.

Best,

NH
 
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