So i have my nieces 2004 Civic EX with about 152k on it. It has had a lot of issues - i bought the car from auction and immediately it started throwing codes. I replaced (in no order). Brakes, front ds hub, caliper, timing belt, alternator, thermostat, plugs, coil packs, oil pump (that was quite the surgery), removed the exhaust manifold and cleaned out the exhaust ports to get positive flow (there was another code i've forgotten since), and have since gotten the car to run pretty well. It continues to throw the P0497 code.

I don't have a smoke machine, but i do have a vacuum pump. My diagnostics tool does not allow 2 way communication, so i can't turn these Evap valves on and off. I replaced the Evaporator Emission Canister Purge Valve (on the throttle body), that didn't fix - code came back almost immediately. I also replaced the vapor canister valve on the cannister. Last thing to replace in that system would be the two way valve. I can go and activate it with a 9 v battery to see if its clicking, but before i do that, 2 questions.

1) how do i troubleshoot the 2 way valve - are there three pins? ground and two sides?

2) what else in the system (cat converter was a possible problem and had previously replaced the upside o2 sensor, but haven't had any issues there for a while) could be creating that low flow evap condition causing the P0497? I get the good hiss from the gas tank when you take the gas cap off, so doubt its the gas cap.

Thanks in advance for any suggestions. I've looked all over these forums and have seen lots of posts on EVAP and P0497, but they all seem to be intermittent.