PNP is Volvoese for park/neutral switch. Different from the micro switch under the center console, the PNP tells the ECU if the selector is in park or neutral. And it also regulates the backup lights. The PNP switch is located close to the battery, covered by the air intake tube.

I suggest finding a Haynes manual for the 850. It covers quite a few good things. Also down load this:
http://www.matthewsvolvosite.com/forums/viewtopic.php?f=1&t=8018

And volvospeed has a good section on repairs also.
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The curise control needs to have a speedometer to work, that could be related so fix that last.
The speedo signal is also routed through the ABS controller. Verify that the ABS light works when you turn the key to pos II. 1996 and newer Volvos have soldering problems with the ABS module and can be repaired.

Klaus
--
Common sense trumps a PhD