What would cause a check engine light to come on while driving on highway?

What is your question?

While heading to work going around 70mph check engine light came on flashing then stayed on, transmission relined and running around 75 mph when finally shifted over. Was not flooring gas pedal when happened just driving normal.

What makes this problem better or worse?

n/a

How long has your 2004 Jeep Grand Cherokee had this problem?

2 days