ASE A6 Electrical Electronics Practice Test
36. A four-cylinder engine's #1 and #4 cylinders are misfiring. According to the schematic diagram above, which of the following is causing these misfires?
- A. There is an open at point A in the system.
- B. There is an open at point B in the system.
- C. There is an open at point C in the system.
- D. There is excessive resistance at point D of the system.
Answer A is wrong. Point A is a common ground for both drivers. Drivers are transistors. The computer uses them to control different actuators, like the coils in the schematic, usually by grounding the control circuit.
Answer B is correct. An open at point B results in no voltage input to the coil and a misfire code at both the number 1 and 4 cylinders.
Answer C is wrong. An open in the 2-3 coil’s power circuit will result in a no-spark problem with that coil.
Answer D is wrong. Resistance in the crankshaft position sensor’s circuit will result in a corrupt signal and, most likely, a no-spark condition at both coils.