On occasion the serve soon message comes up with the yellow wrench. It goes away after turning the vehicle off. I'm wondering how long I have between the message coming up and it being cleared. Is it done in time or miles driven?

 

On some fords 40 ignition cycles without a return.

 

Depeds on the type of DTC. Some take so many drive cycles. The PCM runs some O2 tests only at a constant speed for a certain lenght of time and others not. Pulling the 4WD module fuse turns the wrench ON as soons as you start the vehicle, replace the fuse and it turns OFF.

Once pulled a O2 connector on my old 97 Ranger. No code at all when started.