To change the battery, make sure that the ignition key is not in and take out the back seat bench. You can remove the seat by pressing on the two tabs under both sides of the seat. The battery is on the passenger side. You can just simply replace the battery. However, after the new battery is installed, you may need to synchronize a few things. I have responded to a previous post by attaching a complete list of items that might need to be re-synchronized. You can search this forum by clicking on the "search" link (in the upper right hand side). It's easy to find, just look carefully. Here is a copy-and-paste anyway:
Synchronizing Head Restraints:
If the power supply was interrupted (battery
disconnected or empty), the head restraints are no
longer adjusted automatically. To resynchronize the adjustment feature, turn electronic key in steering lock to position 2, move the seat completely forward and the head restraint fully down, and hold respective buttons for approximately two seconds.
Synchronizing power windows:
If the power supply was interrupted (battery
disconnected or low), the windows cannot be opened or
closed by the Express feature. To resynchronize the express feature, press side of power window switch to resistance point until the window is completely closed and hold for additional 2 seconds. Repeat procedure for each window. The automatic full opening and closing procedure of the windows should now be restored.
Synchronizing sliding/pop-up roof:
If the power supply was interrupted (battery
disconnected or low), or if the sliding/pop-up roof is blocked during closing/opening procedure, the system has to be synchronized. To do so, turn electronic key in steering lock to position 2, move and hold switch in direction (3), until the sliding/pop-up roof is completely raised at rear, and
hold for additional 1 second.
Synchronizing ESP:
If the power supply was interrupted (battery
disconnected or empty), the BAS/ESP malfunction
indicator lamp may be illuminated with the engine
running. Turn steering wheel completely to the left and then to the right. The BAS/ESP malfunction indicator lamp should go out.
Synchronizing remote control:
The remote control may have to be resynchronized, if
the vehicle cannot be locked or unlocked. To synchronize insert electronic key in steering lock.
The remote control should once again be operational.