What do the codes P0600 and P1698 mean and how can you clear them from a Dodge Grand Caravan?

My father has a 1996 Dodge Caravan code P1698 comes up, check engine light on most of time, and dash lights off most of time. When dash lights come on, the check engine light stays on also. Can you tell me what my next step is to resolve this problem without a mechanic telling me it is something it is not that may cost more than the actual issue?