Gmc Sierra Problems!!?

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a friend has a 2000 Gmc SIERRA and it won't go into four wheel drive anymore.someone took it thru the mood runs and ever sine then the four wheel drive wont lock it.We are going to need it so. What could be the problem?? Can anyone please help?

 

[Molson02536]

a friend has a 2000 Gmc SIERRA and it won't go into four wheel drive anymore.someone took it thru the mood runs and ever sine then the four wheel drive wont lock it.We are going to need it so. What could be the problem?? Can anyone please help?

If you mean the front axle will not lock, inspect the front actuator. It's electric so inspect the wire harness and leads to the Actuator and repair or replace any damaged parts. Unplug the connector and test for voltage at the plug..if you have voltage than the actuator is gone...no voltage its the fuse...or relay.

The Actuator on front differential locks in the front axles. The transfer case just transfer power to front wheels in either low or high gear ratio settings when selection is made. The Encoder Motor recieves this input from TCCM, makes the proper motor output selection and sends a signal back to the TCCM of the status of the shift. Somehere in here I THINK is where your problem lies. It is PROBABALLY a bad voltage getting back to the TCCM from the Encoder. COULD be wiring. Could be a faulty ground. So the front differential, driveshaft and internal transfer case components are "freewheeling" in 2wd.

The other common thing to go bad is the switch it self, Pop open your switch and look at these points. If they are cracked and broken, you should be able to re-solder them and give that a shot. If they go out, it might look like its working.. flashing and all but really is doing nuttin.

Good luck and keep us posted on your 4wd issues.