2001 Blazer won't shift into 4WD

I have a 2001 Chevy Blazer that will not shift into 4WD, 4HI or auto 4WD. I've tried everything, shifting from a stop, shifting when in neutral. It just stays in 2WD.
Does anyone have suggestions of what to check? I'm not that car savvy, I know some women are, but I'm not. I do good to check my oil, have it changed on a regular basis, have my tires rotated, you get the idea. But I am a single mother tight on money and the dealership I bought it at told me it would be $40-80 to diagnose what is wrong, then will depend on what is wrong as to how much it would be to fix it. My car is not under warranty so I'm sure they would charge an arm and a leg even if it is just to reconnect a vaccuum hose that is loose or something!
If it's anything too complicated to check, I'm sure I could print it out and find a guy friend to help me check it, so I'm open to ANY suggestions of things to check. Thanks in advance.
Amy
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Not too familiar with the Blazer. I have fixed a couple of the switches on the Silverado's that do the same thing. GM has got some cold soldier joints on the board connection where the wire harness plugs in. On the silverado, resoldering it solves the problem and also fixes the service 4WD light.
Brian

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jazmyn54 wrote:

Unfortunately, you really don't have much choice but to get it scanned for ATC (automatic transfer case) codes and see what comes up as a fault code. If you do have the (auto4hi) button, then you can only see codes with a scanner. The other Blazer 4x4 system without the automatic t/case can be diagnosed without using a scanner.
I would hazard a guess that you may need a software update. We get a lot of the newer 4x4 systems in that lock up and won't do anything....in many cases, there has been updated software released for it.
If the lights flash when you try to engage auto4hi or 4hi, but it won't complete the shift, then you may have a problem with the vacuum solenoid that engages the front diff. I've seen a number of them go south. This solenoid is actually mounted to the firewall right above the distributor at the rear of the engine. A quick check is to disconnect both vacuum hoses from the solenoid, verify there is vacuum on one of them (engine running) and then manually stick them together and see if the 4x4 completes it's shift. If so, you most likely need a new solenoid (this assumes that this year uses this system, I can't quite remember which years they used this, but I believe your vehicle is in that range)
Ian
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Well, after talking with a couple friends, no one felt comfortable messing with my car. So I ended up taking it to the GM dealership my friend works at instead of the Chevy dealership I bought it from.
But like you said Ian, I would need to take it in anyway. A few months back I replaced my battery because it kept dying and I'd have to find someone to jump start me. The old battery was grotesquely bulged but I did not see the mess it had left on my battery shelf. Turns out the battery had leaked and the acid had dripped down on to my actuator cable and ate it up pretty good!
Helps to have connections, only had to pay the $27 for the part and the labor is going to be covered in a purchase of a certain alcoholic beverage, lol. Guys are so easy to please ;)
Thanks everyone for your help and suggestions!
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