ok, these codes have to do with the throttle body sensor which has nothing to do with the ignition spark.
651 - maximum govern speed override
652 - fuel rev limit
both of these codes are related to each other and happen if the engine over rev's for more than 0.150 sec. When it detects this condition the MIL light will turn on during this condition.

Are you sure that was all the codes?
generally if the ecm is bad it will display a code for that, if there are no other codes it has to be something you did when you reconnected the harness's or something. If it ran before you R&R'd the flexplate i'd say it was something you disconnected during that process or something related.