Oscilloscope Patterns and Waveforms

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.




Trouble judgement by spark plug conditions