Jeep Repair: 1999 Jeep GC Speedometer, powertrain control module, crankshaft position sensor

Question
The speedometer and tach just quit indicating. The odometer still works, but it is digital, whereas the speedometer and tach are analog. Will I have to get a whole instrument cluster, or is there a simple fix?

Answer
The speedometer gets it's signal from a sensor on the transmission called the output speed sensor.  Typically, the car will go in to a limp mode only allowing it to be driven in second gear.  

The tachometer signal is sent by the crankshaft position sensor.  When it quits the engine will not run.  

When the Output sensor fails you will get a check engine light.  When the crank sensor fails you may or may not get a check engine light depending on frequency of failure and whether or not it fails completely and never restarts for a second time.

The instrument cluster can be recalibrated using the dealer scan tool.  I would recomend having that tried before replacing any parts.  If the technician cannot recalibrate it then again I would not recomend just throwing a Mechanical Instrument Cluster (MIC) at it because these signals are frequently tied in to the powertrain control module which is also the same module that handles transmission operation.

You may luck out with a new MIC but I would recomend spending the money on diagnostics before throwing this kind of part at the jeep.
Doug