Need help with troubleshooting 4 wheel drive issues. Possibly vacuum related.

It is active all the time. I have replaced the rubber hoses and the TC vacuum switch. The Blazer went into 4wh then 4 wl then got stuck in 4 wh. I put it on 4 jack stands, started it, then pulled the battery tray and connected the vacuum line to the actuator. It engaged the cable properly. I just disconnected the vacuum line to keep it out of 4 wh. I had just put a new engine in it and was testing the 4 wd out. It survived Hurricane Matthew but was under a considerable amount of water. Going to check for voltage to the encoder motor tomorrow as well as clean connections. I have a Haynes and Chilton manual but they severely lack much of the info I need. I have pieced together a massive amount of info from reading forums. Will try reading the codes from the OBD pins A & F tommorrow. Even with the vacuum disconnected from the actuator , the 4 wh light stays on. I may try to erase the stored codes as well with a few forum tricks after the Test. I don't want to put a locking pull cable on the actuator , but it sure would eliminate most of the problem. 4 wl will not engage. The amber light blinks repeatedly and returns to green 4wh. Does the 4 wheel low operate from the reserve vacuum in the vacuum canister? Does the encoder motor tell the vehicle to switch between 4 wl and 4 wh? The switch is telling the TCCM to change because I can hear the clicks in the area where all of the modules are located (behind passenger dash) which I have dismantled to gain access to unplug all of the modules.

1 > In a quiet inviorment, key on engine off transmission in neutral .. Select 4x4 range and listen for encoder motor to make the shift .. IF no noise try tapping on the encoder (transfer case shift) motor with small hammer or similar tool .. Does shift motor respond to tapping? 2 > Simple test to 'confirm' 4x4 engagement .. When driving on dry pavement and turning steering wheel sharply left or right, do you feel the vehicle 'buck' as it should IF 4x4 is actually engaged?

Yes it made noise. Yes it engaged 4 wl in neutral after flashing amber (while running I think) but the amber light did not stay on in 4 wl it stayed green. It went back to 4 wh but it still didn't disengage the 4wh after pressing the button (green) again. Disconnected the vacuum line again to disable 4 wh. Electrical issue? Haven't tried erasing codes yet. Of note with ign on not running and in neutral, the encoder motor does not make noise while pressing the amber side of the switch. What tells the encoder motor to go from 2 wh to 2 wl or 2 wd? Going to check for voltage on the blk/w & r/blk wires on the front axle (sensor??) Hard to dianose alone or without a wiring and vacuum diagram.

You'll need a helper .. As suggested - IF tapping on shift motor completes the shift sequence .. Replace shift motor assembly! .. Good luck!

Sorry but I was outside working on the vacuum routing. I appreciate your efforts and wish I had your knowledge and experience. I heard it moving without tapping. Thanks. Will edit this upon fixing it through a process of elimination. woodboyusa@yahoo.com

I sent you some mail... IF you replaced the vacuum hoses going to the vacuum switch on the transfer case individually - it's very possible the hoses are not arranged properly now... That's the reason you need to confirm it is actually in 4wd by test driving! .. Front axle actuator may indeed be pulled into engaged position but the transfer case may not actually be in 4wd... In any event, good luck with it.. pushrod out.