The check engine light came on on my 96 Volvo 960. It was followed by the W and E lights flashing near my shifter, and the arrow light (transmission) flashing on the dash. I stopped the car and fiddled with the shifter (moved it back and forth) and when I started it back up, no more flashing W, E or arrow lights until I got close to home, when the flashing lights started again. The error code reported is PO715 (speed sensor input error). Where is the speed sensor? Is it part of the PNP switch? I can;t find a part number.

 

Try this- with car parked engine off go from park to low about 20 times like your sawing a log.
CLeans the contacts in the PNP switch
I had the same problem,symptoms and codes on mine this cured it.

 

That makes the lights go out when I start it but within a few minutes the check engine light comes on again and if I start driving, all the flashing starts again before I hit the end of my street.

 

You need to get the codes pulled.

 

The code is PO715.

 

That code is for the transmission speed sensor.