That small orange or yellow icon on your dashboard can appear without warning. Sometimes your car still seems to run fine, and other times there’s a noticeable change in performance. Either way, the check engine light is your car’s way of saying something isn’t right. It could be a minor issue, or it might point to a developing problem that could lead to expensive repairs if left alone.
Here are some of the most common reasons this light turns on, and why it’s important to have it diagnosed promptly.
1. Loose or Faulty Gas Cap
This might sound too simple, but it’s true, a loose gas cap is one of the most frequent triggers for the check engine light. If the cap isn’t sealed properly, it can cause a drop in pressure within the fuel system. That disrupts the evaporative emissions system and triggers a fault code.
Before assuming the worst, always check to make sure your gas cap is tight. If the light doesn’t go off after a few drives, it’s time to have the system checked.
2. Oxygen Sensor Failure
The oxygen sensor measures how much unburned oxygen is in your car’s exhaust. This data helps the engine control module (ECM) adjust the fuel-air mixture for efficiency and emissions. A faulty sensor can cause poor fuel economy, rough idling, and eventually damage to other components like the catalytic converter.
Most vehicles have more than one oxygen sensor, and the faulty one must be identified and replaced to restore proper function.
3. Catalytic Converter Trouble
The catalytic converter reduces harmful emissions by converting gases like carbon monoxide into less toxic substances. If it becomes clogged or damaged, the engine may lose power, the exhaust may smell like sulfur, or the vehicle may fail an emissions test.
A failing catalytic converter can be the result of long-term neglect, often caused by unresolved issues like a bad oxygen sensor or engine misfire. Once it’s damaged, replacement is the only solution.
4. Engine Misfires
When one or more cylinders fail to fire properly, the result is called a misfire. This usually causes the check engine light to flash, especially if it happens continuously. You might also feel the car hesitate, shake, or lose power.
Misfires can be caused by worn spark plugs, failing ignition coils, fuel delivery issues, or internal engine problems. Driving with active misfires can quickly damage the catalytic converter, so immediate diagnostic is important.
5. Mass Airflow Sensor Issues
The mass airflow (MAF) sensor measures how much air is entering the engine so the ECM can calculate the correct amount of fuel to inject. If this sensor fails or gets dirty, the engine may run rich or lean, causing poor acceleration, stalling, or reduced gas mileage.
While sometimes the sensor can be cleaned, a full replacement is often needed once it begins to malfunction consistently.
6. Problems with the EVAP System
The evaporative emissions control (EVAP) system traps fuel vapors from escaping into the air. This closed system includes the gas cap, purge valve, vent valve, and several hoses. If there’s a leak or a faulty component, the ECM will turn on the check engine light.
EVAP codes don’t usually cause immediate driveability issues, but they will affect emissions and may prevent your car from passing an inspection. It’s best to have them diagnosed and repaired, even if the car still runs normally.
What to Do When the Light Comes On
If the check engine light is solid and your car feels normal, it’s still important to schedule a diagnostic check soon. Driving for days or weeks without addressing the issue can lead to further damage or reduced performance.
If the light is flashing, it indicates a serious problem, often related to engine misfires, that needs immediate attention. In that case, it’s best to pull over safely, shut off the engine, and call for assistance.
Let Autoworks of Issaquah Diagnose It the Right Way
When your check engine light comes on, don’t guess and get answers. At Autoworks of Issaquah in Issaquah, WA, our technicians use advanced diagnostic tools to read fault codes, pinpoint the exact issue, and recommend the right repair.
Whether it’s something simple or more involved, we’ll help you get back on the road safely and with confidence.