I did pick up a bidirectional scan tool, thanks to Amazon Prime. Xtool Anyscan A30D. Here's what I've learned so far:
-Pump turns on when commanded.
-Both check valves are clicking
-With the pump off, valves closed, engine off, both pressure sensors are reading 14.2 PSI (atmospheric).
-With the pump and valves on, engine not running, pressures sensors are reading about 16 PSI. Don't know if that's normal or not. I wonder if it's higher than expected and it's pointing to clogged air injection ports.
-P0411 is the only DTC being set.
Only thing I'm puzzled on is the tool has two sets of readings; one has "pressure sensors" bank 1 and 2, and both are showing the 14.2 or 16. The other group says "pressure reading" bank 1 and 2, but those are showing zero.
I cleared the DTC to see if it comes back. I'm hoping that if it can stay off long enough to get through the e-check station, it turns out the test result is good for a year, so maybe if can cross my fingers and get it to pass, we have about 2 1/2 years to save up some pennies to hopefully get something else.
If it is the clogged ports, is it in any way possible to spray some solvent into the injection ports, like that stuff for cleaning direct injection intake deposits? Cleaning them up "by the book" involves taking the cat converter and exhaust manifold off, and replacing the exhaust manifold studs and gasket. Not sure if I'm up to attempting that.