If everything is hooked up right and the ecu is good, you would get a code if a sensor or the vtec solenoid was bad. If you arent getting a code, I'm supposing everything is ok and it might not be engaging due to insufficient oil pressure, coolant temp, or speed over 20mph. Try revving from under the hood while toggling +12v to the solenoid and see if there isnt a difference in sound. I've heard that the x-over isnt very noticable in the sohc, but if you're looking hard, you probably should pick it up. When we tried that test with my b16, it screamed when it got 12v to the solenoid. unfortunately my ecu doesnt want to make it work when it's supposed to
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