I have an LS/v-tec, 00 b16 head and 97 ls block, The v-tec is wired perfectly, I have oil in it (full), my ECU engaged v-tec in my friend's car so I know its not that. I checked all the plugs and wires, everything works. I even checked it with a test light and the ECU sends power when i reach 5800 rpm. I have no codes poping out. I clean the screen on the v-tec unit itself. I don't know what else to check.

 

you forgot to check one thing.... the SEARCH button..... that has been covered atleast 20 times...just search for "vtec problems" or "vtec not working"

 

I had a similar problem, it turned of to be the TPS, and I disconnected on of the O2 censors from the ECU, and now VTEC engages just fine and you might wanna check oil pressure switch as well