What causes the engine idle to drop from 900 to 400 rpm when brakes are applied?

What is your question?

Sometimes the engine dies. This occurs in Park, and in Drive when coming to a stop in traffic. It happens about 2/3 of the time. The vacuum hoses appear to be in good condition.Car runs fine when driving. Please tell me how to retrieve the codes at home, if that would help. There is no "service engine" indicator on. I read something about a faulty EGR valve in an old post. Suggestions? Thanks in advance for helping me help a friend.