A knock noise was present from the engine at around 2000 rpm, accompanied by an occasional puff of black smoke before the engine continued to run normally.

A 2012 Mazda BT-50 UP 3.2L diesel was presented with an intermittent engine knock under light to moderate load, occurring between 1300 and 2500 rpm. A puff of black smoke followed the knock on occasion. The issue did not present at idle or in first gear, and additional load did not make it worse. The fault would happen once per acceleration event, and could recur if the driver backed off below 2000 rpm and accelerated again.