4th Gen accord with h22a jdm

My vtec worked for 1 day and now my car redlines at 6500 and the only code
i get is 23 with my p13 ecu and vtec will not engage when i turn the car off
the check engine light goes out but as soon as i drive it comes back on and the
only code i get is 23 everything else is fine

code 23 is the knock sensor i knoe
but how can i check the vtec pressure switch
and the vtec solenoid

 

you're vtec solenoid wire may have come loose, that happened to mine before, you could check for loose connections, but I would fix CELs first although it should not affect vtec as far as I know, it seems like a good start, you will have sluggish performance below 5500 rpm, if your knock sensor is broken you could always buy a p28 and chip it