CRT Warning Light

[Ccantine]

Hi folks. 2003 international with a t444e and Allison 2000. Was on a 6 hour trip and this CRTdm warning light came on. Stayed on for about an hour and then went off. I think it’s a soot sensor, definitely aftermarket. Not sure what the warning light means, or whether it’s something I should be concerned about. All in all, the bus ran great. Any thoughts on this? Thank you.

Picture is hard to see - it’s a Johnson Matthey CRTdm Diagnostic Midule