Oscilloscope Patterns and Waveforms

INSPECTION USING AN OSCILLOSCOPE




- Trouble detection by heated oxygen sensor output pulse.




- When normal
Engine condition: No-load idling after warm-up




- No injection in one cylinder
Engine condition: No-load idling after warm-up
Pulse detected: Pulse cycle extremely short




- No ignition in one cylinder
Engine condition: No-load idling after warm-up
Pulse detected:
Pulse cycle longer than normal pulse
Rich spike caused by unburned gas in misfiring cylinder observed




- Exhaust gas flown in cylinder
Engine condition: No-load idling after warm-up
Pulse detected: Pulse width and cycle irregular




- Plunger sticking detection using an oscilloscope.




- When normal: Counter electromotive voltage A, generated when the three-way solenoid valve or the fuel injector is turned off from on, shows irregular convergence because induced electromotive voltage B, generated by the plunger return operation, is added to it.




- When plunger stuck: When the plunger is stuck, pulse convergence is smooth because no induced electromotive voltage B is generated.