Originally Posted by wschotty

There was a service bulletin for the crank sensor on these Jeeps. I wasn't sure if mine had been replaced so I bought a spare just in case. I've been carrying a spare for over 10 years, of course never had a problem with it.

Some reading regarding the instructions/TSB:
https://www.jeepforum.com/threads/crd-crankshaft-position-sensor.3717857/

Best scan software:
Appcar DiagFCA (PC)
OBD JScan (android)