The great thing about purchasing a Certified Used Honda Hybrid from a dealership is the awesome warranty that goes along with it. This used car warranty is just like a warranty that you get with a new car in that is covers pretty much everything from the motor, to the trans; pretty much all of the powertrain.
Honda Motor Co. states that they will fix or totally replace all parts and accessories that have a defect. So if there is a major failure, you have absolutely nothing to pay since the certified hybrid comes with a warranty. The Powertrain coverage varies, but what is covered under this is the engine, transmission, and anything associated with the drive train.
A 1-year, 12,000 mile guarantee is good on non-powertrain stuff like the air conditioning, heating, fuel system, suspension; things of that nature.
source: http://automobiles.honda.com/certified-used/warranty.aspx