We have an 08 Impala..... we have the maddening code for the Secondary Injection Incorrect Flow... The pump motor is working just fine and can be actuated by a scanner.... BUT still have the code....is there a way to "test" the solenoid to see if it'* good before spending a boatload to replace it?

PO411?

Yes....that is the one.... when I command the pump to come on, it does..... so I'm thinking the solenoid is bad...but is there a way to test it before spending quite a bit for a new one to find out "if" that is it.

Have you checked to see if anything is plugged up and if the pump actually blows air?

Yes, in fact I had another pump that I switched just to make sure and made sure the hoses were clear.