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I'm building a P75 to run an 89 Accord LXi. In searching for how to operate my IABs, I also ran into the all out p75->p72 conversion, which would give me VTEC/knock connections, and decided that those would be nice to use for use for I/O for later projects.

In looking into the actual electrical connections, I've learned that the VTEC solenoid is a simple 12V when on, and the ECU checks for 14-30 ohms to dectect whether it is connected.

I know there is a VTEC switch/pressure sensor, but am curious as to what are the electrical characteristics for the ECU circuit it is connected to. Does it just detect on/off, does it actually read a pressure, and if so, what voltage range/resolution can it measure?

I know that the knock sensors have an interface board that connects to the ECU via a connector, I was wondering what those connectors are wired into the ECU side of the connection? If I have to, I guess I can trace the leads, but without a clue as to what is on the knock board side of the connection, I might not be able to fully understand them.

Ideally, I will have enough outputs to operate a mux and then have access to a bunch of inputs.

Anybody who could point me in the right direction would be appreciated.

the wiki has the knock board location info...


the VTEC signal is just a high-side switch on the ECU, and the ohm reading on it is for a part of the onboard check function.
the VTP from what I recall is just a switch... (when PSI is => x, apply ground (or +, I don't recall)

but I think all the data I/O ports are all of the same type, so you should be able to use them for I/O but it would take some coding of the ROM... a nice task to undertake.

There might be some knock board layouts out there somewhere... someone might chime in on that.