everything you described there will happen with front wheels not engaged.

you will feel power, you will feel slipping, etc etc

front wheels can still be not engaged. mine werent and i felt all those same things.

 

Tinted; I don't think he will feel the "binding" he described in his last post unless the front wheels are actually engaged and driving. That is not to say that the switch on the front axle is telling the computer such.

 

i have the same issue there was a spilt hose that goes to the solinoid (front anxle) i cut it out and reconnected the hose back. still no 4wd

 

Had same issue with my 2000 the control module under the passenger side kickplate was only clicking every once in a while went to junkyard got another one for 30 buks smeared it with dielectric grease plugd it in been working ever since just my .02 cents good luck

 

OK well I tracked it down... *sigh* sadly it was the first thing I should have checked. Being the pessimist I am, I anticipated it being the BIG stuff being wrong as is usually my luck. Well as it turns out, it was the 4 button selector. I took it out, disassembled it and then reassembled it and 4WD works again lol. I bought a new one at Oreileys Auto Parts just in case the oem one is going bad. The harness must have come a lil loose or something. Thanks for the posts guys. IF I have another 4WD issue, now I have other ideas to look at

 

I just had a similar problem on mine it would go into 4 lo and not 4 hi. Simple to do remove the battery tray hook the battery up to jumper cables to see if you are getting a vaccum at the actuator and trace it back to the leak you are having to the solenoid on the heat sheild center of the engine. mine was a bad solenoid not getting the 10 volts needed. If it has vaccum you will see it or a leak you will probally hear it also the check valve sowetimes goes next to the driver side.