Jeep Wrangler JK 2018 Owner's Manual page 205

GETTING TO KNOW YOUR INSTRUMENT PANEL 203
If your OBD II system is not ready, you should see an
authorized dealer or repair facility. If your vehicle was
recently serviced or had a battery failure or replacement,
you may need to do nothing more than drive your vehicle
as you normally would in order for your OBD II system to
update. A recheck with the above test routine may then
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indicate that the system is now ready.
Regardless of whether your vehicle's OBD II system is
ready or not, if the MIL is illuminated during normal
vehicle operation you should have your vehicle serviced
before going to the I/M station. The I/M station can fail
your vehicle because the MIL is on with the engine
running.