Four Wheel Drive Vacuum Hose Routing
 

I have a question I haven't been able to find a definitive answer. I have two 2001 Blazers and they aren't connected the same. On my 5 speed Blazer the vacuum line from the manifold goes to the secondary air pump. No 4WD but no codes either.

Now on the ZR2 I found the manifold vacuum line connected to the actuator under the battery tray. 4WD works but there are code P0410 and P0418.

What I think should be is that the line from the back of the manifold should be connected to the solenoid that controls the secondary air pump diaphragm and the source for the 4WD actuator should be from the vacuum switch at the transfer case..

The vacuum connection on the manifold is the one the feeds the reservoir on the driver side fender and my question is what does the other connect to?

If I am understanding your question correctly, the other line goes into the passenger compartment and controls the HVAC directional doors. As far as your codes, if the one way check valve fails going to your AIR system, water from the exhaust can get in the pump and if you're in cold climate it can freeze preventing the pump from operating which pops the relay.

Thanks Rock but I think I need to clarify. My HVAC works great but I have been trying to sort out the 4WD and the secondary air pump.

I am trying to get clarification on connections for the hub actuator under the battery tray which I believe should get vacuum from one of the 3 connections on the switch at the transfer case and the secondary air pump solenoid should get its vacuum from the manifold.

I took it to a mechanic for another issue and he said he got the 4WD going and made a new vacuum harness.

You are correct, vacuum from the transfer case switch controls that diaphram under the battery tray. I can't be real helpful on the AIR....don't have it on my ZR2.

Thanks rockp2 for the answer

Found this if it will help.
Attachment 36089