When does DEF injection start?No light with empty tank

I replaced my Adblue heater today. Once it was in I cleared the code. I put my rear lights in and went for a drive to see if the code came back.

2 miles away and I was happy the CEL didnt come on. Then it dawned on me. Shouldn't the adblue sensor be telling me I'm out of adblue? The tank was empty as I didn't want to fill it till I saw my heater sensor code was fixed.

I turned around and drove home. No CEL or DEF light at all.

Maybe it doesn't check it till it's up to operating temp? My thought was it would need to inject urea asap as cold engines tend to spit out more NOX.

Anyway, I filled the DEF tank and put the rear bumper back on. Now I guess I just cross my fingers.

Maybe I should force a regen? Just to clean out any excess soot?

Thoughts?

Your going to have to drive a few hundred miles for all the readiness flags to reset.

Interesting. I guess I'll drive and see what happens. Maybe I'll keep my laptop in the car with the VCDS cable just in case I need to reset something. I'd hate to have a no start condition away from home.