The speedo and odometer on my 93' XJ (4x4 with AX-15 tranny, and NP231 transfer case) do not work, and I bought the jeep this way from the previous owner. All the other gauges in the cluster work. I took out the gauge cluster, and everything looked okay. I removed the speed sensor from the transfer case, and none of the teeth were missing and the connectors weren't dirty and looked fine.

Should I buy a new sensor, or a new gauge cluster? What else could be causing the speedo and odometer to not work? Could it be as simple as a bad ground?

 

Hi

first you should check the continuity of the speed sensor signal wire, it connects to cluster connector pin A5 and pin#3 on VSS

if that passes

check that speed sensor is getting -ve and +ve on IG ON.
Centre pin aka pin#2 is ground
and pin#1 should have +5v on IG ON.

You can also test the VSS - you need a good digital multimeter
remove the VSS from the transmission
insert the pin into the signal and ground wire of the VSS connector from the back
connect signal to +ve of the multimeter and ground to COM
turn the VSS very slowly and you should see +5v and then OPEN/0 and repeat, if you see this the VSS is good. and if all above including the wiring checks out fine, you need to replace the cluster