Check Engine Light ON? Service Engine? Simple Self Troubleshooting Guide

How to diagnose Mercedes-Benz Check Engine Light (CEL) problems.

Is your check engine light on? Is it flashing? Did the check engine light come on while driving? Don’t panic.

When the check engine light turns on in your instrument cluster, the computer on your car has noticed that the engine is not running at its best performance or the sensors being monitored are not providing readings within the default ranges. In return, the Engine Control Unit (ECU) will trigger a fault code in the following format P0001. You can look up these codes yourself to find out what they mean. Follow these steps to troubleshoot your Check Engine Light (CEL), the Service Engine Soon light.

You can read the fault codes and erase the check engine light yourself. You should fix the problem before clearing the Engine Control Unit memory. Otherwise, the check engine light will come back again.

Instructions on how to troubleshoot Check Engine Light / Check Engine light.

To complete this task, you will need a simple OBD II scanner. These diagnostic scanners are a must for all car owners. Within seconds you can find out why the check engine light is on. Here are some of the bestselling OBD II scanners on Amazon, several of them selling for under $15.

Scanner is plugged into the OBD II port right under the steering wheel, above the brake and gas pedals.

Locate OBD II port.
Look under the steering wheel, in the driver’s footwell. Underneath the dashboard is the port where you plug in your OBD II scanner. It is very obvious, and you can’t plug your scanner in the wrong port because it doesn’t fit elsewhere. Watch the following video if you need help locating the OBD II port.
Turn the key to the second position. All the dash lights come on but do not start the car.
Hit READ on the scanner. You will see codes such as P0300. Write all of them down if you have more than one. YOUCANIC full system scanner is shown in the picture below.
If you are having trouble with a Mercedes-Benz, go to www.mercedesmedic.com/faultcodes/ to get an idea of your problem.
If you want to do more research, use the Search function on Mercedes Medic or any other search engine to understand the problem better. On any search engine, enter the manufacturer and the code you got from the scanner. For example Mercedes-Benz P0300

The Check Engine light could sometimes come on for minor issues, such as not tightening the gas cap properly. You don’t want to pay someone $$$ so that they can tell you that, do you? Do yourself a favor and get a scanner like the one mentioned above. The scanner is not going to fix your problem, but it indeed allows you to have a better understanding of what’s wrong with your car. If you have to take your car in for repairs, you will be more knowledgeable and won’t get ripped off (for lack of a better word) by the mechanic. With an OBD II scanner and some research, you will be more prepared and know how serious the problem could be if it is serious at all.

If you plan on repairing and troubleshooting, you may want to consider investing in an advanced OBD II diagnostic scanner.

What should I do if the Check Engine light comes on while driving?

If your check engine light comes on, assess your car’s condition immediately. If you have to drive, watch two crucial displays on your dashboard.

Make sure your engine temperature doesn’t go past the halfway mark. You don’t want your temperature gauge to be in the red, overheating zone.
Monitor your dash to ensure the oil light doesn’t come on. Very unlikely, but if it does, you are in serious trouble. If your oil light comes on, STOP the car immediately. In this case, you would be better off towing the car home or to a mechanic.
On the luxury cars such as Mercedes Benz, BMW, Lexus, and Audi, depending on the reason for the check engine light, the car may go into limp / emergency mode, and the transmission will no longer shift properly. Don’t panic. This is for safety reasons, and to avoid further damage to your car once you make it home, use the OBD II scanner to get the fault codes.

Hopefully, you don’t have any severe problems with your car. If it is a Mercedes-Benz, you can use the search function on Mercedes Medic to see if an article will show you how to fix what is wrong. Once you fix the problem, you can use your scanner again to erase or reset the check engine light. If the problem has been fixed, the Check engine light will stay off. If it comes back again, that means the problem has not been fixed, or there is another problem.

Tip: Most auto part stores have an OBD II scanner to let you borrow to scan your car for FREE. We strongly recommend you get your own OBD II scanner soon; they are relatively inexpensive on Amazon; see here.

Top Reasons Why your Check Engine Light is On.

Loose fuel cap or damaged cap. If the fuel cap is not tight or not sealing properly, the Check Engine light will come on. The car will test the fuel system to ensure it can hold pressure. If it fails this test, then you will get CEL. If you have an OBD II scanner like the one mentioned above, you can know if this is your problem.
Oxygen Sensor O2 Your car has a few oxygen sensors, typically between 2 to 4. They measure the unburned oxygen. You may also get poor fuel economy if your Check Engine Light is on because of the O2 sensor. The input values from the O2 sensor are used to adjust the fuel delivered to the engine. You can get O2 sensors at a fraction of dealer prices on Amazon that will fit Mercedes Benz. Check this one here, for example.
Bad Catalytic Converter If these go bad, they start to get clogged. If that is the case, you will lose much power, and the car will feel sluggish, especially going uphill. You are looking at $200 to $400 for a universal cat and $600 to $1200 for an exact fit.
Mass Air Flow Sensor MAF The MAF measures the air going into the car and, in some cases, the temperature of the air to adjust the fuel mixture ratio properly. They get dirty and malfunction. You may get away with cleaning yours, but a new one may be worth it. You can get one for $50 or even less on Amazon.
Bad Spark Plugs / Wires / Spark Plug Coils Newer cars don’t use spark plug wires. Instead, they use spark plug coils that sit right on top of the spark plug. Either way, if you have an older car with wires or a newer one, these components could cause the check engine light to come on. Your Check engine light will flash on the dash. If you scan the car, you will get a code such as P0300, P0301, or P030* Check these spark plugs on Amazon and read some reviews before you buy.

What is the best scanner to use to diagnose a Mercedes-Benz?

The YOUCANIC full system diagnostic scanner is essential for troubleshooting Mercedes-Benz problems. This powerful diagnostic tool can help identify and diagnose issues with your vehicle’s engine, transmission, brakes, and other critical systems by reading and interpreting fault codes stored in your car’s computer system. With detailed information about the problem, you can make more informed decisions about repairs and maintenance, potentially saving time and money on costly repairs.

In addition to its diagnostic capabilities, the YOUCANIC scanner can also perform diagnostic tests on various systems, including the ABS, airbag, and steering systems, to help pinpoint the root cause of any issues. Whether you’re a DIY mechanic or a professional technician, this tool can help you diagnose and solve even the most complex automotive problems quickly, making it an essential tool for anyone who wants to maintain their Mercedes-Benz and keep it running smoothly years to come. With the YOUCANIC scanner in your toolbox, you can confidently approach any Mercedes-Benz problem, knowing you have the tools and knowledge to tackle any issue.