96 Grand Caravan Speedometer and Tach Problem

The speedo and tach on my wife's 96 GC, 3.8 L mini-van won't activate
every time at start-up. They always (so far) activate when starting up
the next time. I ran Instrument Cluster test and the Ignition Code
Readouts. The Instrument Cluster test was normal. I got two numbers
from the ignition code readout. One indicated that the battery had
been disconnected within the last 50 key starts and the other had to
do with the upstream O2 sensor voltage being shorted to ground.

The battery disconnect code could be related to the problem, so
I cleaned the battery terminals and the ground point near the
dipstick. It helped a little, in that the failures were further apart.

Now I want to check the speedo/ tach speed sensor and connections but
don't know where they are located. Any body know?

Has anyone had this problem and know how to correct it?
Paul

Paul <> cut Phil to respond.