Oscilloscope Patterns and Waveforms

Inspection Using an Oscilloscope




1. Trouble detection by heated oxygen sensor output pulse.




a. When normal (No-load idling after warm-up)




b. No injection in one cylinder (No-load idling after warm-up)
- Pulse cycle extremely short




c. No injection in one cylinder (No-load idling after warm-up)
- Pulse cycle longer than normal pulse
- Rich spike caused by unburned gas in misfiring cylinder observed




d. Exhaust gas flown in cylinder (No-load idling after warm-up)
- Pulse width and cycle irregular




2. Plunger sticking detection




a. 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.




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