In a single-cylinder electronic injector cut-out test, when the injector on the missing cylinder is cut, what happens to the mean pulse width?

• A. PW increases
• B. PW does not change
• C. PW decreases
• D. A fault code is logged

Answer: (B)

Pulse width is the time an individual injector stays open each cycle, meter­ing fuel based on the sensed air mass and engine speed. In a single-cylinder injector cut-out test, you disable one injector to simulate a failed cylinder, but the engine control unit continues to command the remaining injectors according to their own fuel maps for the current operating point. That means the injectors that are still firing keep their prescribed widths, so the average pulse width of the active injectors stays essentially the same. The cut injector simply contributes zero, but among the injectors that are firing, the width remains as programmed, so the measured mean does not change.