try cleaning the PNP switch with the directions on volvospeed, they will act up when it gets cold.

http://www.volvospeed.com/volvo_performance.php

from volvospeed:

The requirement to replace the PNP switch is usually prompted by the up arrow on your instrument cluster flashing, maybe the mode select switch flashing between modes and possibly the turning on of the check engine light. You might also notice that your car is stuck in 3rd gear. The first thing to do for a 313 code recovered from the A-1 diagnostic socket is to clear the code and then do what I call a ratchet cleaning. Move the shift lever from "P" to "L" rapidly 15-20 times, this can clean up the copper contacts on the inside of the PNP switch. Some shops will do the ratchet of the shifter without mention when doing a service, (I do). The changing of the weather from fall to winter also causes the fault to show up a lot.

it may help.

Dan