bluebull

The 06 will lock up in second if you shift it into second manually increasing speed or slowing down. You can use it like a weak engine brake for slowing down. This is also a good practice in slow traffic to keep the transmission cool.
In tow/haul it locks in 3rd then unlock to fourth then lock up.
push button one more time it keeps the transmission from going into 4th and locks up in 3rd.