Dodge Durango 2012 Owner's Manual page 630

628 MAINTAINING YOUR VEHICLE
4. Approximately 15 seconds later, one of two things will
happen:
a. The MIL will flash for about 10 seconds and then
return to being fully illuminated until you turn OFF
the ignition or start the engine. This means that your
vehicle's OBD II system is not ready and you should
not proceed to the I/M station.
b. The MIL will not flash at all and will remain fully
illuminated until you turn OFF the ignition or start the
engine. This means that your vehicle's OBD II system
is ready and you can proceed to the I/M station.
If your OBD II system is not ready, you should see your
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 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.