Elantra suddenly failed to start manually, went to 4S to clean the throttle, and then the fault light came on again. Did 4S say that insensitive oxygen sensors have an effect on startup?

The oxygen sensor detects the oxygen content of the exhaust gas from the engine, and the signal enters the engine computer to adjust the fuel injection quantity, thus realizing closed-loop control.

Damage will lead to high fuel consumption, and the fault light will be on. The engine is unstable.

This fault only appeared after your car cleaned the accelerator, indicating that your three-way catalytic converter is damaged and needs to be cleaned or replaced. It's not necessarily that the oxygen sensor is broken. I hope it works for you.