ASE A6 Electrical Electronics Practice Test
36. A scan indicates the #1 and #4 cylinders of a four-cylinder engine 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 shown above, 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 1-4 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 only.
Answer D is wrong. Resistance in the crankshaft position sensor's circuit causes a corrupt signal. This faulty signal will most likely result in a no-spark condition at either coil.