So I spent the money on this DEF head tester thinking it would easy to just send shop to shop. Take the guess work out of it. Get this thing in and its our usually BB 2017 BBCV engine light on and on dash it says DEF level over percentage. cummins insite codes 4277,4677,3868,6613. So every 1 that has come in it has been a bad DEF head. So hook up the new tool and it shows that [ missing CAN Bus termination resistor, so check harness and terminating resistors . NOT 1 WORD SAYING BAD DEF HEAD. We checked liked it said just for HAHA's and of course everything is fine. change def head problem gone. So for anyone out there looking to buy 1 don't count on it telling you that it has a bad head. Better off just checking wires the old fashion way with a meter. It does check some other stuff but I haven't tested on that yet.
We have about 20 newer (2016-2020) BB transits and we've replaced about 3 DEF multifunction units now. Just got done replacing one yesterday actually because of these same issues and codes. Is there anything on these newer buses that doesn't go bad?