Most Common Reasons Your Check Engine Light is On

January 14th, 2019 by

Gas cap check engine light on gauge cluster

It’s your worst nightmare. Your check engine light has appeared and you’re wondering, “Why is my check engine light flashing?” Don’t panic! There are many reasons for the engine light to come on, and not all require expensive repairs. Here are some of the most common reasons for a check engine light warning in your Mercedes-Benz.

Possible Check Engine Light Meanings

1. Gas Cap

While your gas cap might not seem like the most important piece of equipment in your Mercedes-Benz, it actually plays a pretty important role. It maintains pressure in the engine and prevents fuel vapors from leaking out. In some cases, the gas cap check engine light will come on when the fuel cap has not been tightly secured.  We suggest that you unscrew the gas cap and re-tighten until it clicks, then allow the gas cap check engine light up to a day to reset. A loose, broken, or missing gas cap can cause your vehicle to start jerking and lower its efficiency. If the light remains on after a day, contact us at (909) 891-0121.

2. Oxygen Sensor

The oxygen sensor in your Mercedes-Benz monitors the percentage of unburned oxygen in the exhaust. Over time, the sensor can get covered in ash, thereby reducing its effectiveness and leading to a decrease in gas mileage and an increase in emissions.

3. Catalytic Converter

Your catalytic converter reduces exhaust gases by converting carbon monoxide and other harmful materials into harmless ones. Most failures are due to faults with other items, but a damaged catalytic converter can mean your car will fail its emissions test.

4. Mass Airflow Sensor

The mass airflow sensor allows your car’s computer to know how much fuel is needed based on the amount of air coming into the engine. Faults can decrease efficiency, increase emissions, and cause your car to stall.

5. Spark Plugs and Wires

Spark plugs and wires are responsible for creating the original spark that initiates combustion within your Mercedes-Benz, but they can fail over time. If yours are faulty, misfires will occur.

6. Aftermarket Alarm

If not installed properly, an aftermarket alarm can cause a whole host of issues with your electrical system, including draining the battery and triggering the check engine light.

7. Vacuum Leak

The vacuum system is responsible for a number of functions, including lowering harmful emissions and playing a part in the brake booster. If your check engine light is on, and you notice your car’s idle begins to surge or settles at an unusually high rpm, then you may have an issue with the vacuum system.

8. Exhaust Gas Recirculation Valve Failure

Helping your car be more efficient, the exhaust gas recirculation (ERG) system helps decrease the amount of nitrogen oxide that comes out of the car’s engine. Over time, the ERG system valve can fail or become clogged, setting off the orange engine light.

9. Dead Battery

Your battery helps power all the electrical systems in your car, and if the charge is low, your check engine light may activate. You may need to charge or replace your battery.

Check Engine Light Meaning & Origin

As automotive technology advanced and relied more and more on computers, the check engine light was added. First appearing in the 1980s, this light paired with the onboard computer system. When the electronic-control system finds an issue that it can’t correct, it activates the light. Along with service engine light flashing, the computer will generate and store a “trouble code” that identifies the source of the problem. This code can be read with a code reader at our Ontario dealership.

Steps to Take if Your Service Engine Light is Flashing

For starters, don’t ignore the orange flashing light. It could lead to a dangerous driving situation, as well as permanent vehicle damage. Follow our troubleshooting steps below and then schedule service if needed:

  • Check your vehicle: Look over gauges and other lights for any other signs of a serious problem.
  • Reduce engine demands: Experiencing performance issues? Reduce your speed and lighten your load until you can make it to a service center.
  • Tighten your gas cap: No serious problems to be found? Try tightening your gas cap. Wondering if your check engine light will reset itself? If the gas cap is the issue, it could take a couple of trips to reset.
  • Use mbrace®: If you have the Mercedes me app, you may be able to use remote diagnostics to determine your vehicle’s issue.

Have Your Check Engine Light Diagnosed at Mercedes-Benz of Ontario

Your Mercedes-Benz check engine light is never something you should ignore. While the potential reasons for your check engine light displaying might not sound too serious, any one of these could develop into a much more complex issue over time. Rancho Cucamonga, Ontario, Fontana and Inland Empire drivers should stop by Mercedes-Benz of Ontario to have a Mercedes-Benz Master-Certified technician diagnose your vehicle and have your gas cap check engine light reset. Schedule an appointment today! Have questions about other Mercedes-Benz warning lights? We can help!

Posted in FAQ, Service, Service Tips