Engine Light On? Diagnose the Culprit

A bad sensor can damage components like spark plugs and catalytic converters and cause a car to fail an emissions test.

Fremont, CA: If your check engine light is on, don't panic. It doesn't mean you need to pay for a mechanic's services. Simple and quick fixes can fix the issue. Don't ignore it; get it checked out as soon as possible. The fault code for the light is stored in your car's onboard computer, which can be retrieved using a simple device. Taking care of this yourself can save you money in the long run.

1. Oxygen sensor failure

A failing oxygen sensor in a car triggers the check engine light, measuring unburnt oxygen in the exhaust system. The sensor sends data to the vehicle's computer, regulating the air and fuel mixture. A bad sensor can damage components like spark plugs and catalytic converters and cause a car to fail an emissions test. A quality O2 sensor costs about $175, with labor costs varying depending on the vehicle's make, model, and location.

2. Loose fuel cap

Loose fuel caps can cause the check engine light to appear, as they are crucial for preventing gasoline fumes from leaving the fuel tank and maintaining proper pressure. If the light appears after a fill-up, ensure the cap is not loose or still on the car's roof. Replacing the cap can be affordable, as most auto parts stores carry universal-fit gas caps priced around $15.

3. Catalytic converter failure

A catalytic converter failure can cause a check engine light in a car, converting carbon monoxide from combustion into carbon dioxide. Depending on the make and model, a new converter costs $200-$600. Regular maintenance, like oil changes, is crucial for the converter's function. If you live in a city and drive short distances, take your car on the highway to prevent clogging.

4. Spark plug/ignition coil issues

A check engine light can be triggered by a car's malfunctioning ignition coil or spark plug. Modern vehicles use one coil per cylinder, known as a coil pack. If the car burns diesel, neither ignition coils nor spark plugs are present. Worn or fouled spark plugs can cause engine misfire and hesitation under heavy acceleration, while worn coils can cause unexpected shut-off. Quality spark plugs cost between $10 and $20, while coils are generally in the $50 range.