Not every check engine light means an expensive repair, and not every one is safe to ignore. The light itself doesn't tell you which — but a few details will.
Steady vs. blinking
A steady light means “get it looked at soon.” A blinking or flashing light means the engine is actively misfiring badly enough to dump unburned fuel into the exhaust, which can damage your catalytic converter within minutes. If it's flashing, ease off the gas, avoid highway speeds, and get it looked at right away instead of finishing the drive as planned.
It's a code, not a diagnosis
The light is triggered by one of hundreds of possible trouble codes stored in the car's computer. A code points to a system — not necessarily a part. “Random misfire detected” could mean spark plugs, a coil, a vacuum leak, or something further down the line. Guessing a part and replacing it is how people end up paying for three repairs to fix one problem.
Common low-stakes triggers
A loose or failing gas cap is a surprisingly frequent cause — it throws an evaporative system code that looks alarming but costs nothing to fix. An aging oxygen sensor is another common, moderate-cost cause that isn't urgent.
Common higher-stakes triggers
Misfires and catalytic converter codes are worth taking seriously. Left alone, a misfire can take out the catalytic converter it's protecting, turning a moderate repair into a much more expensive one.
A real diagnostic scan (RR‑7) reads the actual code, checks the freeze-frame data around it, and gives you a plain-English explanation and a quote — before anything gets replaced.