cmn1882

What should I do about this? P1456 EVAP Emission Control System Leak Detected (Fuel Tank System)

FISH22

i dont want to be misleading, but, its very possible its the gas cap, or a warped fuel filler neck...pretty sure this was once an issue with the s2k.

gomarlins3

If it is the fuel cap, it will take a few cycles (trips driving the car) to reset.

According to billman (and he knows his stuff):
P1456 95% chance it was the gas cap.

Utah S2K

Most likely gas cap. OBD-II will request the ECU to shut of the light after three consecutive passes. A pass is considered a period long enough to fully bring the car up to temperature at which time OBD-II will perform a "non-obtrusive" test which is essentially a sub routine that "pings" the sensor or system which created the fault. So after 3 no fault found cylces the light goes out. The DTC will still be stored in what is known as a "freeze frame" for the next 40 warm up cycles. In short. Tighten the cap...

Utah

(Ref: "Getting to Know OBD-II" by Birnbaum 2001)

P.S. If not cap it may have been caused by an ovefill at the pump (which will close a specific check valve and set the code). Don't overfill the S. 3rd on the list an out of round fuel filler neck (Ref: TSB 04-02 all '02's may be effected and I noticed you have an '02)

Billman250

If you grab the handle of the gas cap and tighten it, it may not get tight enough (on cars with an egged filler neck, common on your 2002)

After it clicks a few times, grab the outer edges of the cap and squeeze a little. Then slowly tighten the cap. You'll feel it get tighter.

I'll withdraw my 95% and say 98% chance that is the problem.