My check engine light came on yesterday with a code of p0456 which is a 'small leak in the evap system' according to various sources. I changed out my fuel cap (no change thus far) and I also noticed recently that my heater core is leaking ever so slightly. Would my heater core leak cause that code or would it be something else? If it is something else what should i look for besides the gas cap? Is there a an easy quick fix to stop the heater core leak rather then replacing it? For example use 'k-seal' if it's a minor leak at best? Thank you in advance.