Jaguar Repair: Speedometer/trip computer, service interval, interface unit

Question
I recently replaced my heater core. First trip out of garage the speedometer and trip computer was non-operational(lights come one but no indication). I have a jagual service manual. I tested all powers and found them curect. I jacked the car up and placed on stands. Attached volt meter to yellow wire (pulse) wire from transmitter. When started i have 12.3 volts. When placed in drive and allowed to spin, voltage goes to 12.8 and rises as i increase the speed of the tires. I think its working, but no indication. Any Ideas?

Answer
Hi John,
There are several items tied in to the system. The service Interval Counter, Cruise Control and Trip Computer are connected directly to the yellow lead going to the speedo.
You said you checked all powers. Green power to the Pulse Generator, The Service Interval Counter, The Interface Unit and the Trip Computer? Grounds too? Power from #4 and #7 fuse?
I can't think of anything up front that can interrupt the Speedo/trip Computer.
Howard