i have a 2002 gmc sonoma zr2 and it has 4wd but when i try to engage it it does not engage. The indicate light comes on but it does not engage. It is an electrical switch. I tried putting in a new accuator but that did not seem to help. any other simple fixes if not then any suggestions.

 

is the actuator working?

 

Yes the accuator is working. I think it might be the vacuum lines right in front of the driver door that goes into the fender. i can feel the suction in the hoses. i do not know if they are getting a good seal though because when i got the pickup the lines never were hooked up onto the pickup they were just dangling inside of the hood i then hooked them up to what i assume to be the right places.

 

You may need to perform a complete vacuum hose replacement. Amazon has rolls of vacuum hose for $20 couple dollars. As far as the POS vacuum reservoir in the side fender, mine has the nipple completely broken off. I finally found a diagram with the reservoir and its completely metal. If it's rusted out, there's your problem. Even if you could find a replacement, it's almost impossible to put in because you have to move the ABS manifold. Get a <$10 plastic vacuum reservoir and see if it fixes the inability to hold a vacuum. if it does, you're there. I found a round ball like looking one and it sits in the engine compartment just fine.Bottom line is if you are not assured that your system is intact, you cant troubleshoot the actuator, switches, etc.