Ultrasonic Sensor Troubles

In your shoes, I'd try simulating the code to see if it is doing what you expect. At this point we still don't know if the problem is hardware or software.

I don't suppose you have access to an oscilloscope so you can see exactly what's going on?

If you don't have a simulator you can try a trial version of one from https://www.oshonsoft.com/


Torben