Flashing vs. Steady Check Engine Light
Steady light
A steady light means the computer found a problem that needs attention but is not causing immediate damage. Many steady codes, like small EVAP leaks, are low urgency. Read the code soon and look it up.
Flashing light
A flashing light almost always means a severe misfire. Unburned fuel is going into the exhaust and can overheat the catalytic converter within minutes. Reduce speed, avoid hard acceleration, pull over when safe, and turn off the engine. Have it towed or drive only a very short distance gently.
Other warning lights matter more
If the temperature gauge reads hot, the oil pressure light comes on, or the brake warning light is lit, stop driving. These can mean immediate engine or brake danger regardless of the check engine light.
What to do next
Read the code with a scanner (see our scanner guide), then look it up here. Misfire codes like P0300 are the most common reason for a flashing light.