I have a 854 with 88k that I drive infrequently as well. The PNP switch in the transmission can collect dust and junk if the car sits for a while, causing a fault when you can easily clean it out by moving the shifter. Even if the switch is cleaned, the fault code is permanent until reset. With the key ON (but without engine running), move the gearshift from P to L (back and forth) a couple of times to clean the contacts. The gearshift is electronically controlled, not directly connected to the tranny. Anyway, I had the same problems when I let my 850 sit for a month. You'll have to reset the code anyway. Check out the site for resetting transmission codes. If it's a non-turbo, you can do it in the driveway without tools. Good luck!!!