While your car might not be able to talk, it certainly communicates with you through chimes, icons, and messages. One signal you should never disregard is the check engine light. This light turns on when your car’s onboard computer detects an issue.
If your check engine light comes on, don’t freak out—it doesn’t necessarily mean an expensive repair. Sometimes, the problems behind a check engine light are simple and quick to fix. However, don’t ignore it either. It’s best to get it checked out as soon as you can.
Among the most common reasons for a check engine light are:
Keep in mind that the fault code triggering the light is stored in the car’s computer system. You can retrieve this code with a simple device to understand what’s wrong. Doing this yourself can save you money in the long run.
A failing oxygen sensor often triggers the check engine light. This sensor measures the amount of unburnt oxygen in the car’s exhaust system and sends this data to the vehicle’s computer, which then regulates the air and fuel mixture entering the cylinders. While the engine will keep running if the O2 sensor needs to be replaced, it will burn more fuel than usual. Over time, a faulty O2 sensor can damage parts like spark plugs and the catalytic converter and may cause the car to fail emissions tests.
A quality O2 sensor typically costs around $175, but the labor cost varies based on the car’s make, model, and your location. Remember, most modern cars have more than one O2 sensor.
A loose fuel cap is another common reason for the check engine light to come on. The cap is a vital part of the car’s fuel system, preventing gasoline fumes from escaping and keeping the system correctly pressurized. If the check engine light turns on immediately after a fill-up, check to ensure the cap isn’t loose or still on the car’s roof. Sometimes, the cap might need replacement, but it’s a cheap fix. Universal-fit gas caps usually cost about $15.
Catalytic converter issues can also trigger the check engine light. The catalytic converter, part of the exhaust system, turns carbon monoxide from combustion into carbon dioxide. Its failure can be prevented with regular maintenance, like timely oil changes. A new catalytic converter costs between $200 and $600, depending on the car model.
Make sure to perform regular maintenance and occasionally drive on the highway to keep the catalytic converter from getting clogged. Watch out for unusual sounds or smoke from the exhaust.
Problems with spark plugs and ignition coils can also cause the check engine light to come on. The ignition coil generates the electricity needed by the spark plugs to ignite the fuel and air mixture in the cylinders. Modern vehicles usually have one coil per cylinder. A malfunctioning coil can trigger the check engine light, but remember, diesel cars don’t have ignition coils or spark plugs.
Worn or fouled spark plugs can cause issues like engine misfire and hesitation during acceleration. A bad coil can cause similar symptoms and may even shut off the car unexpectedly. Quality spark plugs cost between $10 and $20, and coils are usually around $50. Changing spark plugs is easier than it sounds.
A bad spark plug wire can also illuminate the check engine light. These wires transfer electricity from the coil to the spark plug. Most cars use one wire per cylinder, though some older models have more. Symptoms of faulty spark plug wires include rough idling, decreased engine performance, and lower gas mileage. A set of plug wires typically costs about $50 and is easy to replace.
The mass airflow (MAF) sensor can also trigger the check engine light. This sensor monitors how much air enters the engine, affecting its ability to adjust to altitude changes. Symptoms of MAF failure include rough idle, trouble starting, and sudden changes in throttle response, as well as reduced gas mileage and stalling. A late-model MAF sensor costs between $120 and $150.
Improperly installed aftermarket alarm systems can cause problems, including triggering the check engine light, draining the battery, and even preventing the car from starting. Have the alarm fixed, reinstalled, or replaced by a competent mechanic to avoid these issues.
Vacuum system issues can also light up the check engine light. The vacuum system serves various functions, including operating the brake booster and reducing emissions. Symptoms of a vacuum leak include surging or unusually high idle. Vacuum hoses can dry out and crack over time, especially when exposed to extreme temperatures. Tracing the source of a vacuum leak can be time-consuming and costly if done by a mechanic.
The exhaust gas recirculation (EGR) system reduces nitrogen oxide emissions and helps the engine run efficiently by directing exhaust gases back into the combustion chambers. A clogged EGR can trigger the check engine light. If you’re mechanically inclined, cleaning or replacing the EGR valve yourself can save you money.
A dead battery might trigger both the battery light and the check engine light. Car batteries are now maintenance-free and last longer than before, but a quality battery still costs at least $100. Changing or charging a battery is straightforward, though newer cars might have the battery buried under plastic covers. Disconnecting the battery typically resets the stereo system, so get the code from your dealer beforehand.
Modern cars have sophisticated systems, but you often need an aftermarket device to decipher why the check engine light is on. Many people take their cars to the dealership for this, but it’s the most expensive option. Investing in an OBD II scanner, costing less than $40, can be a more economical choice.
Find your car’s OBD II port, usually in the driver’s footwell, and plug in the scanner. The error codes from the car’s ECU will appear on the screen. Sometimes, these codes need some research to decipher. Error codes guide you in figuring out what’s wrong, though they don’t always provide the complete picture.
Professional-grade scanners are more accurate but also costly. You can rely on auto parts stores for free diagnostics, but owning a scanner saves time and money while increasing your car knowledge. Ensure the scanner you buy is compatible with your car.
The check engine light gives you an idea of car issues but doesn’t replace a skilled mechanic or regular maintenance. Don’t wait for the light to come on to maintain your car. Routine upkeep and timely diagnostics in response to new signs and symptoms are essential. Familiarity with your car’s needs will save time and money, and regular maintenance might prevent that orange engine light from ever lighting up.