I have been throwing CEL code 21 (VTEC Solenoid) for a week now, and I can't figure out why. The code only comes on the first time I start the car, when it's cold. If I drive it, park it, and restart it within ~4 hours, to where the engine is still somewhat warm, it does NOT come on, and VTEC works. If the CEL is on, no VTEC. I pulled the solenoid, and it did not look bad, here is a video of me testing it, you can hear it clicking as it should:

When I pulled it, the filter didn't appear that dirty, but I cleaned it anyway as well as the rest of the assembly. The oil dipstick was halfway up, so I filled it to the top, and nothing changed.
Is the solenoid on its way out?

 

Read this, try suggestions here.

https://honda-tech.com/zerothread/1956456

That would be the cheapest thing to try first.

 

I've called around and all I can find is the CRC CO Contact Cleaner, I'll give that a try though

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by GI8U2racing &raquo;</TD></TR><TR><TD CLASS="quote">I've called around and all I can find is the CRC CO Contact Cleaner, I'll give that a try though</TD></TR></TABLE>

Pull the VSS and see if it has a green color on any of the 3 pins. If so, I'd be willing to bet that's your problem.