jbowers:

Thanks for input.

The "EGR"(?) valve in question has a 2-conductor connector to what appears to be a ceramic covered device, perhaps a solenoid. However, by-passing the device with the inlet vacuum hose to the outlet vacuum hose turns the air pump on, whether the 2-c connector is connected or not. I assume valve works from an external signal opening the valve to permit the vacuum to extend to the air pump solenoid valve.
Speculating further, I suppose the air pump pumps fresh air into the manifold to "lean" the exhaust mixture whenever the exhaust gas is otherwise too "rich", as determined by either the exhaust O2 sensor or the cat O2 sensor. If The sensor says the mixture is too "rich", I suspect the ECU sends its signal via the 2-C connection to the valve solenoid which opens the valve, permitting the vacuum to go to the air pump solenoid valve and turns the pump on. Perhaps this also somehow signals the pump to turn on simultaneously with the vacuum valve opening. Does this make sense? I have already confessed to being a "brickhead, brickboard dummy", so any ideas or comments are gratefully accepted!
--
L R Hicks