MB Medic Mercedes-Benz Repair Guides, Service, How To DIY
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In this guide (5 sections)
How to use the OBD-II, Bluetooth, and Your Phone to troubleshoot your Mercedes-Benz
All Mercedes-Benz cars manufactured after 1996 are equipped with an OBD-II port, mandated by federal regulations. OBD stands for On-Board Diagnosis.
The OBD-II port allows you access to your car’s Engine Control Unit (ECU), which monitors, RPMs, sensors, emissions, mileage speed, and various other parameters. When there is a problem with the car, the ECU triggers a Diagnostic Trouble Code (DTC) or Fault Code by illuminating the Service Engine / Check engine on your instrument cluster. If the Check Engine Light greeted you, you could retrieve the codes using your phone (iPhone or Android) and a Bluetooth Adapter as a scanner. You can use a device such as Veepeak Mini WiFi OBD2 OBDII OBD II Scanner Scan Tool Adapter or any OBD-II Bluetooth Adapter on Amazon Best Selling Code Reader list.
If the Check Engine or Service Engine Soon light is on your car and is staying on or flashing, here is what you need to do.
How to connect the Bluetooth Adapter to the OBD-II port and your Smartphone
1. Locate the OBD-II port on your car. It is located under the dashboard on the driver’s side. The port is typically either black or white. Look above the brake pedal, and you can see it. The port has sixteen pins. Some of the pins may be missing depending on the signal protocol used by the manufacturer. This port is required by federal law and will work with any scan tool that is OBD-II compatible.
2. Plug the Bluetooth adapter into the OBD II port. Ensure that the lights on your Bluetooth adapter turn on.
3. Pair your phone with the adapter. Go to the settings of your phone, and turn on Bluetooth. Then search for Bluetooth devices. You will see an OBD II device discovered. Click on it, and you should be asked for a pairing code. Try 1234 or 0000. If these two codes don’t work, read the manual for the Bluetooth adapter to find out what code the manufacturer used.
4. Go to the Play Market or App Store and download a free OBD II app that will allow you to pair it with your OBD-II Bluetooth diagnostic scanner. We would recommend you try Torque App.
5. Download and open your App to ensure it is connected to the Bluetooth adapter. You can stream live engine data, such as RPMs, temperature, and engine load. More importantly, you can hit Read Fault Codes and retrieve the trouble codes for your Mercedes-Benz.
6. Once you see the error code list, click the Menu button and hit Clear / Erase Fault Codes. Please note that you should only delete the fault codes if the problem has been repaired. If you erase the fault codes without fixing the problem, the check engine light will revert. Depending on what triggered the check engine light initially, it may turn on immediately, or it could take a few days.
Before you hit clear
Two things leave with the code, and neither one comes back on its own.
The first is your inspection readiness. Your car runs a set of self tests called readiness monitors, and an inspection station checks that they have finished. Clearing codes with a scan tool is one of the recognized reasons a car reads as not ready, the same as having just disconnected the battery. The monitors only return to ready once the car completes the drive cycles that run each test, which can take days of ordinary driving rather than a quick trip around the block, and a car whose required monitors are not ready does not pass. The tolerance varies by state. New York, for example, allows one monitor to be not ready on 2001 and newer cars. So if your inspection is next week, clearing the code today can cost you the appointment even though the repair was done properly.
The second is the freeze frame. When the fault was first recorded, the module saved a snapshot of what the engine was doing at that moment, including values like engine speed, load, and coolant temperature. That snapshot is often what tells a technician whether the fault happened cold, under load, or at idle. Clearing the code erases it. If you are handing the car to someone else to diagnose, write the code down and photograph the live data first, or simply leave it alone and let them read it themselves.
Benefits of using Bluetooth to check the engine light
The Bluetooth adapters are great as not only can they read and erase the service engine light, but they can also be used to stream real-time information. A Bluetooth adapter paired with a good app can provide valuable information such as:
- Stream Realtime Information
- Check / Read Fault Codes DTC
- See Test Results
- Provide Graphing
- Display a tachometer or accelerometer
- Record your 0-60 or 0-100 mph times.
- Stream RPM
- Fuel Flow Rates
- The temperature of the coolant, oil, or intake air
Depending on the adapter you use, you may also be able to store profiles and get fuel economy readings and horsepower.
One habit worth keeping: unplug the adapter when you are done with it. Many of the inexpensive ones never go to sleep and keep drawing current from the port while the car is parked, which matters on a car that sits for a week or on a battery that is already tired. If you want to leave one fitted permanently, look for one that advertises a sleep mode, or fit it on a switched adapter.
Conclusion
Using an OBD-II Bluetooth Adapter as a scan tool is a great way to troubleshoot your Mercedes-Benz via the OBD-II port. You will be able to read and clear the fault codes (diagnostic trouble codes), and you can use your phone to check if you are driving efficiently and determine if you are ready for the emissions test.
Note that these Bluetooth OBDII scanners only read and erase the check engine light. If you need to read and clear codes from other control units such as ABS, SRS, ETS, TCU, and more, you will need a full system scanner such as the YOUCANIC UCAN-II Pro, which reaches every module on the car rather than just the engine, and covers what Xentry covers apart from online VIN coding.
Before you buy parts, scan every control module, not just the engine. It shows the root fault behind the warning lights and tells you whether the problem is still active. See how to do a full health check.
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