I have a 1996 Chevy blazer. It has push button 4 wheel drive. The 4 low stopped working it just blinks and goes off. I have replaced the actuator and the encoder motor. I just got a vacuum switch for it and i looked at mine and the 3 lines go over the transfer case and they are cut. One of the lines has one in front of it and I hooked them together and went down the road and when I took the dip stick out about 2 quarts came out like a water fountain. Im guessing that is a vent tube or something. I need to know where them 3 lines come off of the vacuum switch. I talked to everyone and no one knows. I look under one in a parking lot and all three go to the front of the vehicle. My 4 wheel drive worked b4 so I really dont think them lines being cut will stop the 4 low from engaging. Every once in a while after I take it out of 4 wheel drive the front passenger tire will make a humming noise like it isn't disengaging all the way and when i put in and back out of 4 wheel drive it goes away.

 

Have a look at the Tech Article (DIY) section for the NP233 threads. There are vacuum diagrams as well as schematics there that should provide you with the information you need to get the lines hooked up properly.

As far as it not shifting into 4LO... Are you slightly moving while attempting to shift to 4LO? Have you tried to pull the codes (OBD2 Non-Automatic Transfer Case Diagnostics)?

As far as a no mode shift goes, here is the diagnostic steps:

1. Check TCCM for stored codes. See RETRIEVING DIAGNOSTIC TROUBLE CODES. If any DTCs are present, go to appropriate DTC test. If no DTCs are present, go to next step.
2. Test drive to confirm 4HI to 4LOW range shin does not operate. If 4LOW status lamp does not flash while attempting range shin, go to next step. if 4LOW status lamp flashes for 30 seconds while attempting range shift, check Green/White wire between 4WD selector switch and TCCM harness connector for open circuit. Repair as necessary.
3. Turn ignition on. Measure voltage at TCCM harness connector terminal No. C3 while pressing 4LOW button. If battery voltage exists when button is pressed, go to next step. If battery voltage does not exist when button is pressed, go to step 5).
4. Measure resistance between TCCM harness connector terminals No. C10, D10, D12, D13 (Black wires) and ground. If resistance is greater than 2 ohms, repair open suspect ground Back) wire. If resistance is less than 2 ohms, replace TCCM.
5. Measure resistance of Green/White wire between TCCM harness connector terminals No. C3 and 4WD selector switch harness connector. If resistance of circuit is greater than one ohm, repair open circuit as necessary. If circuit is one ohm or less, replace 4WD selector switch.

 

Not moving at all and tried while moving slow and reverse nothing works. I have a scanner and took it to a shop and no codes at all.

 

You cannot scan your TCCM with a scan tool. You must do it following the directions I posted above.