Check engine light came on along with check gas cap

Even if light goes off should store codes you will have to retest

Check for codes & diagnose the new problem with the VSC

Tune-Ups ! --remember those back in the early 1980's, some
25 years ago,your not up to speed,you only get spark plugs

I have no idea why any parts were installed

You always check for codes & use them to
diagnose the system with the fault

You may need a professional scan tool along on a road
test to look at data as well as get caught up on some
maintenance

Take the vehicle to a qualified repair shop an have the EVAP system smoke tested , this will find the leak . Too many thing's that could cause your problem . You don't want to keep replacing parts do you ? Could be a stuck open purge solenoid , a leak in one of the vapor lines , the part the gas cap screws into, vent valve stuck open . Service engine light on ? have checked for DTC'S - diagnostic trouble codes . You'll probably fine a evap code for a large leak.

When you replaced the cap, did you reset the "check engine" light. The problem codes stay in the memory until you reset them. To reset, you can disconnect the battery or remove the fuses that power the computer. The fuses will be marked, with CP or ECH or some similar marking. They may have a number behind it. You can take all these fuses out for about 5 minutes or disconnect the battery for 5 minutes. When you restart watch the light, it should be out. If it comes back on in the first minute or so you still have a problem. Check the code again. Likely the light will stay off once you reset it.

Thanks for using FixYa.

Gaker

Did you change the gas cap with a Honda gas cap? Tighten it at least three clicks?
Also, Honda recommends that you never top off the tank when getting gas (only go to the click-off of the pump; otherwise you can get back flow into the system that will cause the code).
Tightening or replacing the cap will not immediately cause the light to go off; it can take up to three days of driving for the light to reset.
To check if your readiness codes (emission system) are set, turn the ignition to ON (II), without starting the engine. The Malfunction Indicator Lamp will come on for 20 seconds. If it then goes off, the readiness codes are set. If it blinks 5 times, the readiness codes are not set.
You can, of course, try resetting your engine light to see if it will come back on (which it probably will). I believe the procedure is:
Turn off the engine.
Press and hold the Select/Reset knob (odometer) in the instrument panel, then turn the ignition switch to ON (II).
Hold the knob for approximately ten seconds until the indicator resets.

Hope this helps you.

Make sure the gas cap is on tightly. A loose or faulty gas cap can cause an intermittent check engine light. Hope this helped and best wishes.

wow thermostat >>>> shucks i believe its evep emissions code like faulty gas cap ....you can reset any computer the chck eng light will come on in 50 to 100 miles if not fixed....

You need to Replace your Cas Cap. The Seal is bd on it and is allowing air into the Fuel Tank Causing Both Dash Lights. This should solve your Problem.

P0456 = EVAP Emissions Control System Leak Very Small

Is the gas cap on tight or is the seal damaged? If it needs replacement, get it from the dealer.