One problem related to automatic transmission control module has been reported for the 2006 Toyota Sienna. The most recently reported issues are listed below. Please also check out the statistics and reliability analysis of the 2006 Toyota Sienna based on all problems reported for the 2006 Sienna.
Transmission sluggish vehicle delay when changing to 2nd & 3rd gears. Van uses excessive amounts of gasoline. Very poor gas mileage. When I took vehicle to dealership they reprogrammed engine control module r&r however after driving car for 2weeks problem began again.