I have 2006 Crv awd...195K...been throwing check engine lights for last few months...changed vtec solenoid, and then knock sensor and now new code is P0422....says evap....not sure what next step is...please help...thanks..

 

welcome to the forum. hope this will help with your trouble shooting. https://www.engine-codes.com/p0422.html

 

P0422 or P0420 is catalyst is below threshold or efficiency
Check for vacuum leaks, check for exhaust leaks, throw in a bottle or two of fuel injector cleaner
Check readings of both up stream and down stream O2 sensors, check fuel trims both short and long term trims.
Install spark plug anti-foulers on O2 sensors to back the O2 sensor.
Change O2 sensors (without anti-foulers)
Last if all else fails, replace the cat.
Good luck

 

yeh based on the way you say it happened immediately after the knock sensor was replaced, i think the issue is before the engine, so i suspect a vacuum leak.
if its the same as my model, 2003-2006, I had a major issue where my air assist valve was broken, allowing air to always enter the air assist system.
This system is supposed to only let extra air in when cold, in order to help atomise the fuel at the injector heads. it routes unmetered air ( basically a vacuum leak) in quite a substantial amount to the heads of the injectors to help it atomise.
It is spring loaded open, adn the heat form the coolant causes wax to expand (liek a thermostat) whcih pushed it closed. ITs basically a designed vacuum leak and if u dont maintanin it as vigorously as u do a coolant thermostat, it will totaly ruin the EVAP systems idea of what is going on.
Its a huge vacuum leak.

So just try plugging the hose to it (with a bolt) and reset the ECU (unplug battery for a while) and see if it helps.