Flashing vs. solid
Mechanics treat these very differently: solid means “get it looked at this week”, flashing means “an active misfire is happening right now.”
A flashing (not solid) check engine light signals an active misfire that can damage your catalytic converter.
Light is flashing, not solid
Rough idle noticed too
A flashing light signals a misfire severe enough to overheat the catalytic converter.
The most common root cause of a misfire-triggered flashing light.
Less common, same flashing-light pattern.
Mechanics treat these very differently: solid means “get it looked at this week”, flashing means “an active misfire is happening right now.”