Once I put my key in the ignition and turn the car on what are the sequence of events that take place?

Question

Once I put my key in the ignition and turn the car on what are the sequence of events that take place?

In: 753

Answer 1

This is one of those ELI5 subjects that could be like twenty words or five thousand.

Fundamentally the key closes the starter circuit and turns the engine until the cylinders fire as normal.

But in the brief moments between turning the key to the on position and the start position the computer (if it’s a fuel injected car) is running through dozens of operations; cycling the injectors, starting the fuel pump, checking fuel rail pressure, checking crank position, cam position, getting readings from the O2 sensors ahead of and behind the catalytic converter, checking transmission position, brake position, and a BUNCH of other stuff, and that’s before the engine even fires up.