Grade Logic Control: Ascending Control
WARNING: This page is about a different car, the 2011 Honda Insight and 2010 Honda Insight. However, it is still accessible from the selected car via links, so may be relevant.
When the PCM determines that the vehicle is climbing a hill in the D and S positions, the system selects the most suitable shift schedule based on the steepness of the grade so the vehicle can run smoothly and have more power when needed.