Good question. Each of the 8 readiness monitors have different protocol or driving conditions-requirements. Usually 5 or 6 will set fairly fast. Yours being a 08 model can only have 1 unset readiness monitor. A day or 2 of normal driving should do the trick. Keep the tank around 1/2 full because the evap. monitor won't run if the tanks near full. Try driving at highway speeds above 50 for 10 to 15 minutes also.