Why is the Check Engine Light Blinking?

On your dash, an illuminated engine light is a warning that something is wrong.  If the check engine light blinking, you may be damaging engine components by continuing to drive. This is definitely something to take seriously, but is it an emergency?

Is This An Emergency Situation?

A blinking light says the problem is big and it’s getting worse. That’s an emergency that requires immediate attention. It is good to find a safe place where you have phone service.  You’ll want to phone your dealership or mechanic to determine whether the car is safe to drive. It may need to be towed to prevent ruining your engine, according to mechanics at the Earnhardt Lexus dealership.

A steady light does not mean that the problem is an emergency unless the temperature gauge is also registering a problem. If the car is overheating, you don’t want to keep driving. Likewise, if there is a burning smell, then the steady light may mean the problem is too big for you to keep driving.

What Causes an Engine Light to Come On?

The ECU, electronic control unit, is the computerized brain of your engine.  It will turn the light on after it has interpreted a trouble code. With a code reader, a mechanic can determine what is causing the problem.  This could be a faulty sensor or a faulty part. There’s a big difference.

Why Is My Check Engine Light On? | The Family Handyman
Source: The Family Handyman

Manufacturers have added the ability of the light to blink or flash in order to make it clear that the problem has passed the point of simple repair.  A blinking light indicates that the problem has turned into an emergency.

1. Faulty Sensor

There are many sensors in the car to monitor how the engine is operating.  Sensors control the coolant, the air temperature, the exhaust temperature, and the blend of fuel and air.  If a sensor goes bad, the ECU will recognize that and signal you.  Replacing that sensor may be all that is needed.  Once the new sensor is recognized, the ECU can be sure the engine is operating as it should.

The oxygen sensor is especially critical. It can cause an increase in emissions if it becomes covered in ash over time.  Likewise, the mass airflow sensor can become faulty. This causes a poor air-to-fuel ratio and increases emissions. In addition to triggering the engine light, you may notice that your car has a tendency to stall.

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. Faulty Engine Part 

When parts are faulty, this can lead to a systemic problem.  One error can cause a ripple effect, sending damage throughout the system. That’s why you can’t ignore a blinking engine light. 

The ECU makes calculations continuously that affect fuel injection.  Cylinders may be misfiring.  Fuel injectors may have gone bad.  Spark plugs may be faulty. Coils may be damaged.  The system may be overheating.  Each of these problems is bad as a stand-alone item. It will be much worse if driving continues despite the warnings.

4. Faulty Engine Exhaust System

It could be a problem with exhaust emissions.  The exhaust gas recirculation system is designed to reduce nitrogen oxide. The ERG system valve can be faulty, causing the engine light to come on. When your catalytic converter is shutting down, the whole system will shut down with it.  This can mean the end of the car engine if it isn’t addressed very quickly. 

5. Dangerous Vacuum Leak

Lesser known than many components, your engine has a vacuum system that helps reduce harmful emissions.  In addition to the blinking engine light, the biggest clue is usually that the car is surging to a high rpm while in idle.

What should you do if your check engine light blinking?

1. Understanding The ECU Code

If you take your car to an auto parts store, they often have a diagnostic scanner that can read the code that is causing the check engine light blinking. However, they won’t have the ability to fix it themselves. They can sell you parts, but you cannot be sure that knowing the code is telling you everything you need to know about the car. Whatever you do, don’t have them turn off the engine light.

2. Take Your Car to a Dealership for Warranty Service

It is highly unlikely that your engine light would come on during the warranty period. However, if this is the case, you need to take your car straight to the dealership. Unless you have skipped vital oil changes, this is one time where your warranty should provide full coverage. 

Final thoughts

The only way to be sure what is wrong is to have a qualified mechanic read the code and make an inspection.  Since a blinking engine light is probably an emergency, it will save you money and possibly save your car engine if you leave your car with a mechanic until the problem is identified and corrected.