Four wheel drive not working properly

Tiny
MATT FLINK
  • MEMBER
  • 2000 CHEVROLET 2500
  • 5.7L
  • V8
  • 4WD
  • AUTOMATIC
  • 200,000 MILES
The truck listed above is a k2500. I am having problems not going into 4-wheel drive, the 4lo light flashes and when its flashing it's in 2wd if I push the 4hi button it will try to engage but go back to 4lo engaged. I replaced the front actuator and the transfer case shift motor along with the TCCM under the dash (used not new). I even just replaced the transfer case itself and put a new switch/sensor whatever you want to call it on top of the transfer case. I am at a total loss ( I can hear the transfer case trying to engage) any input would be greatly appreciated.
Thursday, January 6th, 2022 AT 6:16 PM

1 Reply

Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
Sounds like you replaced all the common components that cause this so we need to start testing the voltage on the circuits so that we can make sure we have the correct voltage in order to move the actuator.

https://www.2carpros.com/articles/how-to-check-wiring

I am assuming at this point that the parts that you replaced are okay, but we can't completely rule this out. The fact that they are used parts is not always an issue, but it is possible that you have another actuator or other part that is doing the same thing. This was a pretty common issue on these trucks.

So, I would suggest we check the voltage and rule everything else out and go from there.

I attached the wiring diagrams below.

Let's start with going to the encoder and checking the voltage on each wire and the motor and let me know what you find.

Thanks
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Friday, January 7th, 2022 AT 4:10 PM

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