To check the SCR system the 30 minute test drive is most likely needed to be done AFTER turning off DEF dosing.

This is to empty the SCR cat of NH3 so the NOx sensors - pre and post cat can be checked - no NH3 (DEF) - the NOx ppm readings should be very close to the same from both sensors.

If the pre cat sensor ppm is lower than the post cat - then most likely it is suspect, as it lives right behind the DFP and the high regeneration temps. This could cause efficiency faults, MIL on, and perhaps the no-start warning countdown IMO.