The check engine light comes on when the powertrain computer detects a fault that could affect emissions or driveability. How the light behaves tells you how urgent it is.
Steady Light
A stored fault the computer wants looked at, but not an emergency. Causes range from a loose gas cap to an oxygen sensor, an EVAP leak, or a small misfire. Drive gently and get it diagnosed within a few days, and note anything unusual in how the car feels.
Flashing Light
An active, severe misfire. Raw fuel is passing into the exhaust, where it can overheat and destroy the catalytic converter in a short distance. Ease off the accelerator, avoid hard acceleration and high speeds, and get to a shop right away — or have it towed if it's running very rough.
The Gas Cap Myth Has a Grain of Truth
A loose or failed gas cap really can set an EVAP code and a steady light. Tighten it; if the light doesn't clear after a few drives, it's something else.
Why a Code Read Isn't a Diagnosis
The code names a system, not a broken part. Testing that system is what tells you which component actually failed — see our check engine light diagnosis.
Check Engine Light Help for Albuquerque's North Valley
We're at 4201 4th St NW in the North Valley. If you've got a Bernalillo County emissions test coming up, a check engine light will fail it — see emissions repair.