bill graham

Truck in a chevy dealership, would not go into 4wd,lights blinking,only all-wheel drive worked, first told that the modulator was bad,they changed that then said the activator was bad, will both go bad at the same time, looks to me like they changed the modultor and it was not bad, are this things that come up on the truck computer. Billlooks like $1200.

jeverett

Does your truck have an auto-trac transfer case (push button) or the lever activated one?

If it's the push button, check the switch. Thats what mine did. I replaced it for $60 and all worked fine. Some people say you can take the switch apart and fix it, but I just got a new one.

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JDFester

If it is the switch type, it is pretty quick to fix yourself if you are handy with a soldering iron. There were two cold solder joints in mine; took about 5 minutes to get the switch out of the truck, another 5 to fix it, and about 3 to put it back. 4wd has worked fine since!