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Check Engine Light On? Here’s What to Do

One of the best ways to deal with a check engine light (CEL) is to understand what it means and what courses of action to consider when it lights up.

AAMCO Lee's Summit  | 10/06/2021  | Auto Repair & Maintenance

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Check Engine Light On? Here’s What to Do

There are many things that drivers hope never to have to experience while they’re out on the road. One of those things is the sudden appearance of the check engine light (CEL). Not only does it mean that possible repairs (and repair bills) are likely forthcoming, but the light can mean so many things it’s impossible to decipher without taking the vehicle into a repair shop.

What Is the Check Engine Light? What Is Its Function?

The check engine light (CEL) sits among an array of lights on your dashboard. All the lights have particular functions. Some remind you which systems are active such as headlights or high beams, and others offer warnings of malfunctions and other problems that need immediate attention. It is a critical part of your vehicle’s On-board Diagnostics system (OBD).

The CEL is somewhat less specific in what it denotes; its primary function is to prompt you to have a qualified mechanic or technician check the engine for a fault or problem detected by the OBD. A CEL appears in two separate forms—steady and blinking—to denote how serious a problem may be.

Steady “Check Engine” Light

If you see the CEL as a steady light, a problem has been detected but is not urgent. That doesn’t mean you can ignore it, but the issue does not put you in imminent danger while on the road.

Flashing “Check Engine” Light

When you see the light flashing, your vehicle is experiencing an urgent and critical engine problem that you need to have looked at without delay. A flashing Check Engine Light isn’t just a warning; it’s an urgent call to action.

Top 6 Reasons Your CEL Will Come On

1) Loose Gas Cap

Let’s start with the most basic issue that causes the CEL to illuminate: a loose gas cap. If that’s the case, then simply putting it back on correctly will fix the problem.

2) Failing Catalytic Converter

A failing or malfunctioning catalytic converter is a more concerning problem and can result in your vehicle’s emissions not being broken down properly, resulting in diminished engine performance and overheating. Replacing a catalytic converter can also be pricey. 

3) Faulty Oxygen Sensor

The oxygen sensor registers the amount of unburned oxygen in the exhaust system. When it malfunctions, the engine believes there isn’t enough oxygen. As the engine works harder to compensate,  increased fuel consumption and lower overall efficiency may result. If the CEL is on and you notice your vehicle is guzzling more gas than usual, the oxygen sensor may be the culprit.

4) Damaged Spark Plugs

The spark plugs ignite the mixture of fuel and air that enters the combustion chamber. If they are damaged or faulty, you might get a CEL, especially when starting the vehicle.

5) Faulty Mass Air Flow Sensor

The airflow sensor determines how much fuel is needed to make your engine run properly and efficiently. If the sensor is off, improper amounts of fuel will enter the fuel system—either too much or too little—and create serious problems.

6) Bad Transmission

The transmission is not your engine, but it is linked with the engine; it transfers power from the engine to push torque to the wheels to move the vehicle. If your OBD detects an issue with the transmission, it may express itself in the form of a check engine light.

What to Do If Check Engine Light Comes On

If the CEL is steady and not flashing, first check your gas cap, especially if you see the CEL right after you’ve topped up the gas tank. If the cap is secure and the CEL hasn’t gone away, —do not ignore it.

Many drivers have the habit of thinking that the vehicle is just being sensitive. Because a vehicle appears to drive normally when the CEL illuminates, this warning light is often ignored. The best course of action should be getting it to an auto shop for an OBD-II scan to determine what’s wrong.

If you have a flashing CEL, there’s no time to lose. If you’re driving and very close to an auto shop, go straight there. If you’re on the road or at home, call for assistance. Driving with a flashing CEL is dangerous.

Why Maintenance Matters

The best way to prevent the illumination of the CEL is regular maintenance on your vehicle. 

  • Follow your vehicle’s recommended maintenance schedule
  • Service your vehicle at least once a year
  • Attend safety inspections on time if mandated by your home state
  • Never ignore your check engine light

Check Engine Light On? Let Us Help

Schedule an appointment with AAMCO Lee’s Summit today to ensure your vehicle’s health and safety should you ever see your CEL light flash on. 

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