P1456 is a code set when the computer detects a small leak in the fuel-
evaporative emissions control system. This is NOT the gas-cap leak code!
The usual cause is a corroded and damaged control solenoid in the canister
For some bizarre reason, Honda decided it was a good idea to put the EVAP
canister and its control solenoids under the car at the rear, where it's
guaranteed to get encrusted with salt and moisture.
Troubleshooting is complicated, expensive, and often not worth the effort.
I've compiled a list of Honda docs here, which you can print out and bring
to the dealer to have them solve this for you, if you wish.
In certain /very rare/ instances, it is possible for an internal short in
the solenoid-control electrics to damage the engine's computer, so it's
probably unwise to allow this condition to continue for any length of time.
If you choose to leave it alone, chances are the ECM will be OK, but this
situation can affect your emissions testing, depending on where you're
located, and if you have a smog check to begin with.
when you re-fuel, does the gas cap seem looser than when you tigtened
it? if so, try a new gas cap, and make sure it's tight. despite what
it says in the honda tsb's, or what the computer diagnostic says, the
gas cap seems to work lose, and when it does, it sets this code. the
new cap fixed my 96 accord wagon.
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