No Upshift Into Overdrive
WARNING: This page is about a different car, the 2002 Dodge Intrepid, 2002 Chrysler Intrepid, 2002 Chrysler Concorde, and 2002 Chrysler 300M. However, it is still accessible from the selected car via links, so may be relevant.
Possible cause: engine coolant temperature low, worn or leaking overdrive and/or 2-4 clutch or accumulator seals or faulty overdrive switch or circuit.