P0446
 

2006 ford explorer xlt 2wd v6
check engine light on, I already scanned P0446 is the code.
front valve is working and rear solenoid too
gas cap tight, but today I run with out the gas cap and the gas cap light didn't come on.
I live in Puerto Rico during the day Temperature is around 90's I erase the code and no code during the whole day, but at night or early in the morning during the first start of the day check engine comes on with the same code.