Blog Car Care Advice Top 6 Causes For A Mercedes Check Engine Light (+ How to Fix)
Car Care Advice

Top 6 Causes For A Mercedes Check Engine Light (+ How to Fix)

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Is the Mercedes check engine light causing concern? 
We’ve all been there!

It’s a fairly common issue with a few potential causes. Some are an easy fix, like a loose gas cap, while others could be more costly. 

Read on to discover the possible causes, how to reset the check engine light, and more.

This Article Contains: 

Let’s jump in.

What Causes the Mercedes Check Engine Light to Activate?

The Mercedes Benz check engine light, sometimes called the engine management light, generally activates when there’s an issue with the engine or fuel system system. Although there are lots of potential causes, we’ve listed a few common ones: 

1. Loose Gas Cap

A loose gas cap could be the reason why your engine management light is activating. 

If your fuel cap isn’t secured correctly, is damaged, or missing, it can reduce fuel pressure and allow fuel vapor to escape, triggering the warning light. Leaking fuel vapor is toxic and a major contributor to air pollution. Fortunately, it’s an easy fix that shouldn’t take more than a few minutes. 

2. Defective Mass Airflow Sensor (MAF)

The mass airflow sensor measures the air flowing into the engine to help determine the correct air-fuel mixture. 

Driving with a faulty MAF can lead to an engine misfire and reduce your fuel efficiency as well as engine performance, activating the engine warning light. If left unchecked, it can lead to a potentially costly repair, such as replacing the catalytic converter

3. Faulty Oxygen Sensor (O2 sensor)

The oxygen sensor, or the O2 sensor, monitors the level of unburned oxygen in the exhaust gas and provides feedback to the Engine Control Unit (ECU). 

Since this part is in constant contact with hot exhaust gas, it can wear out over time. Once the oxygen sensor starts acting up, the Engine Control Unit may supply the incorrect amount of fuel, affecting fuel efficiency and emissions. If the engine receives too little fuel, it creates the risk of total engine failure, while too much fuel will reduce your fuel economy, create excessive smoke, and activate the engine light. 

4. Failing Catalytic Converter

The catalytic converter converts toxic carbon monoxide in the exhaust gas to harmless carbon dioxide. The catalytic converter can become clogged with time, especially in higher-mileage Mercedes vehicles.

Aside from activating the check engine warning light in Mercedes vehicles, a reduction in vehicle performance and an increase in emissions are two other telltale signs of a failing catalytic converter.

5. Worn Spark Plug or Spark Plug Wire

Each spark plug ignites the air-fuel mixture in the cylinder, which turns the crankshaft and allows your vehicle to run. A worn spark plug or spark plug wire can lead to an engine misfire, reduced fuel economy, poor engine performance, and an active engine light. Eventually, it may prevent the engine from running at all.

6. Malfunctioning Ignition Coil

The ignition coil transforms the low voltage from the battery into a high voltage needed to fire the spark plug. If an ignition coil is acting up, it can trigger the engine warning light and lead to rough idling, reduced engine power, and engine misfires.

Curious about what should you do if the light turns on?
Let’s find out.

What to Do if Your Mercedes Check Engine Light Turns On?

Under normal circumstances, your check engine warning light will activate and stay illuminated. However, depending on the severity of the issue, that can change. Here’s the breakdown on a case-by-case basis:

A. Illuminates Under Certain Circumstances

If the check engine light activates intermittently, drive at a reduced speed and pay special attention to how your vehicle performs when the light is on. In most cases, this signifies that something is about to fail. If there are any clear signs that something’s wrong, avoid driving and make a booking with a certified technician.

B. Check Engine Light Is Permanently On

This means your car’s diagnostics system has detected a fault in one of your engine components. Even if your car still feels alright to drive, it’s best not to risk a costly repair and bring it in as soon as possible.

C. The Check Engine Light Flashes

A flashing check engine light signifies that something has gone seriously wrong. In most instances, your engine is misfiring, and unburned fuel has worked into the exhaust system. This puts additional stress on other components, such as the catalytic converter. If you see a flashing check engine light, your best bet is to drive at a reduced speed and pull over as soon as it’s safe to do so. Then either have your car towed or arrange for a mobile mechanic.

Next, let’s see how to reset the check engine light in a Mercedes Benz.

How to Reset the Check Engine Light

The best way to reset the check engine light in Mercedes vehicles is to address the underlying issue. Once you’ve addressed the problem, the check engine light should automatically reset. However, if you believe you’ve fixed the problem, you can use an OBD-II scanner to retrieve and clear the diagnostics code from your car’s computer.

You can also temporarily remove the code by disconnecting the negative terminal on your car battery (indicated by the black cap and the negative (-) symbol) for one minute. But, if the problem persists, the light will reactivate, and you’ll need a professional to look at it. 

Note: Be sure to wear safety equipment when interacting with your car battery.

Coming up next are the costs for a check engine light diagnosis.

How Much Does it Cost to Have a Mercedes Check Engine Light Diagnosed?

Generally, diagnosing a Mercedes check engine light costs between $86 and $138, depending on the Mercedes Benz model. However, the cost of the repairs will vary according to the part that needs replacing.

Wrapping Up

There are many potential reasons behind a check engine light, from a worn spark plug to a faulty oxygen sensor. While some problems, like a loose fuel cap, are easily solved, booking a mechanic as soon as possible is best. 

And why risk an expensive engine repair when you could have a mobile auto repair service like AutoNation Mobile Service come to your driveway? 

Our expert technicians will tackle the check engine light diagnosis and address the problem in no time. We’re available seven days a week, offer easy online booking, and provide a 12,000-mile | 12-month warranty on all repairs. 

Contact us today for a quote.