Going from memory here, so I hope it's right:

Engine off, key in position 2

Left temperature setting HIGH
Right temperature setting LOW

Key to position 0

Press and hold REST. While holding REST, turn key to position 2. The left side of the display should change to read P1, and some number will appear on the right.

Pres ECON to advance the left side to P2. Write down the number on the right.

IMPORTANT: Break this number down into powers of two. If it already contains the value 16, adding 16 to it will not have the desired result, and there's nothing to do. Just turn the key back to position 0 to end the version coding menu. Otherwise:

Press the right-side temperature up button (red arrow) until you add 16 to this number. Press and hold the REST button >1 second.

Key to position 0 ends the sequence, and returns N22 to normal. Key to position 2 and reset the temperatures to 72 by pressing up and down simultaneousely on each side.