Diagnostics

Reading the fault codes, understanding what each one points to and clearing the light safely.

The Diagnostics screen has three tabs: Read errors, Clear Errors and History. This is where you find out why the check engine light came on.

  1. Get the car ready

    Park and leave the key on with the engine off. The app refuses to start the scan with the vehicle moving, for safety and because the answers are more reliable with the car stationary.

  2. Choose the scan mode

    Tap Diagnose my car and choose between Quick, Basic, Advanced and Professional. Quick and Basic cover what the standard defines and serve most cases. Advanced and Professional query more modules of the car and take longer.

    The same sheet shows the OBD profile for diagnostics, with the Suggested tag on the profile matching your car; Change profile lets you choose another one by generation and engine. The sheet also reminds you to park safely and to keep the key on with the engine off, and warns that some vehicles return fewer results on the deeper scans, because of manufacturer restrictions.

    On the deeper modes the app requires you to confirm a warning before going on. If a mode shows as Feature unavailable for your vehicle, the manufacturer-specific commands are not mapped in the database yet; Request inclusion registers the request, and Quick and Basic still cover the standard codes.

  3. Read the result

    The codes appear split into Pending Faults, Confirmed Faults and Permanent Faults, or the screen says No faults detected. Tap a code to open its detail.

    The detail carries Details, Symptoms, Cause and Solution, as well as the Snapshot shortcut, which opens the freeze frame of that error, obd-codes.com, shown only for the codes that site covers, Search the web and Learn more. The description of the codes is always in English, as set out in SAE J2012.

  4. Understand what the code points to

    A code names the symptom the ECU observed, not the part to replace. P0420, for instance, means catalyst efficiency is below the threshold, a result that can come from a worn catalyst just as much as from a faulty oxygen sensor fitted ahead of a healthy one.

    Before buying parts, open the Snapshot: the conditions recorded at the moment of the fault say more than the code on its own.

  5. Clear the light, when that is appropriate

    On the Clear Errors tab, read the Precautions and follow the Steps to clear: park safely, wait for the connection with the ECU, tap Clear Errors, turn the car off and on again to check whether the light went out, and see a professional to deal with the cause. The app says Clear completed or Clear not completed at the end.

    Clearing the code does not fix the defect: if the cause is still there, the code comes back. Clearing also resets the emission monitors, which need several days of mixed driving to complete again.

  6. Browse the history

    The History tab keeps every Read and every Clear, with the date and the result, Success or failure. Tap a row to reopen that result, or swipe left to delete the record.

If something goes wrong

The scan only runs with the car stationary, for safety and because the answers are more reliable. Park, keep the ignition on and try again.

Run a deeper mode. Quick and Basic read what the standard defines, and some faults are recorded only in modules reached by Advanced or Professional.

There are also lights that do not belong to the engine management: brakes, airbag and ABS usually live in modules of their own, not always reachable through the OBD port.

Coming back is expected while the defect is still there. Clearing wipes the record and turns the light off, without fixing the cause. Use the Snapshot to find out under what conditions the error happens before replacing parts.

It is not advisable. Clearing resets the emission monitors and, in countries where the inspection reads the OBD port, incomplete monitors fail the vehicle on their own, even with nothing wrong with it.

The monitors need several days of mixed driving to complete again.

The deepest mode is a paid plan feature. The Quick and Basic modes stay available and cover the standardized diagnosis.

The description of the codes follows SAE J2012, published in English, and the app shows it as it is. The Symptoms, Cause and Solution sections of the detail, and the search shortcuts, help with the interpretation.

That mode depends on manufacturer-specific commands that are not mapped in the app database yet. Tap Request inclusion to register the request. The Quick and Basic modes stay available and cover every standard OBD-II code.

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