Speedometer and Odometer not working sometimes

[correllkp]

Car is a 1994 940 Sedan 193K miles.

Sometimes the speedometer/odometer simply don't work. When it does work it seems to be accurate according to the GPS. When I start out often the unit is not working and then some minutes later it just starts working.
Researched the various posts on this topic and here's what I have so far.

The wires at the sensor plug seem ok...no corrosion.

Opened up the almost impossible to open black box in trunk (screwdriver and a hammer worked nicely) and disconnected the plug...also disconnected the speedometer plug at the back of the dash. So now I should have, or so I thought, two wires not connected to anything. Ohmed out the G/W wire between the disconnected plugs and was ok. Now, the B/W wire also seemed ok but when I tested for continuity between the wires (with the plugs still disconnected) and the car frame the B/W wire is definitely shorted to the car frame....is this supposed to be this way? Any insight would be appreciated.

[93Regina]

Car is a 1994 940...Any insight would be appreciated.

I use the tach, it always works. Sooner or later, mine, 93-940, starts working.

If computer does not receive a signal, your cruise control will not work. So if cruise works, the signal from rear-end is there.

740/940 Instrument Cluster Repair (1991+)