A flickering check engine light usually means an active misfire, not just a loose gas cap.
Here’s what to check first on your Kia K5/Optima IV—and when to stop driving.
Why a flickering check engine light matters
On your Kia K5/Optima IV, a steady check engine light often points to a sensor or emissions fault, but a flickering light is usually the ECU reporting an active misfire. That unburned fuel can overheat the catalytic converter, so this isn’t a “wait a few weeks” symptom—especially when the idle is rough.
