960/S90/V90 Speedometer problems

[Brianp]

I own a 98 S90 that started having speedometer problems, first the check engine light came on then I noticed the speedometer would be sitting on 0 and I drove away. Because this car is computer controlled the transmission doesn't shift into second until the engine is reving over 3000 rpms. The computer detects the that the speedometer is on 0 so it thinks the car isn't moving so it won't shift. I replaced the speed sensor in the rear housing 3 times and the problem persist. I even cut the wiring plug out of another car just encase that's what was causing the problem. Needless to say the Volvo shop I took it to says it's must be somewhere in the wiring harness. Anyone have a similar problem?

Brian