Acura 2008 TSX Owner's Manual page 264

Automatic Transmission
SHIFT LOCK RELEASE SLOT
4. Insert the key in the shift lock
release slot.
5. Push down on the key while you
move the shift lever out of Park to
neutral.
To release the reverse lockout, move
the shift lever from neutral to
reverse, then to Park.
258
6. Remove the key from the shift
lock release slot, then reinstall the
cover. Make sure the notch on the
cover is on the driver's side. Press
the brake pedal, and restart the
engine.
If you need to use the shift lock
release, it means your vehicle is
developing a problem. Have it
checked by your dealer.