You are NOT being helpful. You made a statement to someone who is having car trouble, that is completely wrong.

As I originally stated; he most definitely has a emissions related problem - a FACT, which out of ignorance, you stated was blatantly wrong. It is likely due to the cold temperature, and the vehicle idling while covered with snow and ice - this will screw with emissions related sensors and equipment, causing the vehicle to set a check engine light. The remedy I suggested is the correct first step.

If I was ignorant about what causes a check engine light to illuminate, I certainly wouldn't attempt to derail the suggestions of knowledgeable people who do.