FehlerfreiOBD-II diagnostics for Android
Know what the warning light means.
Fehlerfrei reads your car’s fault codes through a Bluetooth OBD-II adapter, tells you what they mean in plain language, and clears them when you decide to. The name is German for “fault-free”.
In early testing. Want to try it? Write to support@fehlerfrei.app.
01What it does
Reads fault codes
Stored, pending and permanent codes, with the check-engine lamp status and which control unit reported each one.
Explains them
Each code comes with a description. Pick a car profile and manufacturer-specific codes get their own descriptions too.
Clears them, carefully
Clearing sits behind a confirmation that says what else gets wiped. The app reads again afterwards so you can see what came back.
Shows live data
Engine speed, coolant and oil temperature, fuel trims, voltage and more. Only the values your car supports are listed.
Looks up any code
Type a code from a workshop invoice or a forum post and get its meaning, no adapter needed.
Keeps it on your phone
No account, no ads and no analytics. What the app reads from your car is not sent anywhere.
02Car profiles
Standard OBD-II codes mean the same on every car. Codes starting P1 are the manufacturer’s own, and a generic reader shows them as a bare number.
A car profile fills that gap. The first one covers Porsche Motronic engine control units, including the manufacturer’s own fault numbers where they are known:
| Control unit | Typical cars | Codes |
|---|---|---|
| DME 7.8 | 987 Boxster and Cayman, 997 Carrera | 334 |
| DME 7.2 | 986 Boxster, 996 Carrera with e-gas | 144 |
| DME 5.2.2 | Early 986 Boxster, 996 Carrera | 150 |
More makes will follow. On any other car the app works as a generic OBD-II reader.
03Screens
Screens show the built-in demo car, with made-up codes and values.
04What you need, and the limits
An adapter
An ELM327-compatible Bluetooth Classic adapter, such as the OBDLink LX or MX+. Pair it in Android’s Bluetooth settings first. Bluetooth LE and Wi-Fi adapters are not supported yet.
A car with OBD-II
Most petrol cars from about 2001 and diesels from about 2004 in Europe, and from 1996 in the US. Other markets vary.
Engine first
The app covers control units that answer standard OBD-II requests, usually the engine. Gearbox, ABS and airbag units often need a brand-specific tool.
Not a repair
Clearing a code does not fix its cause. Fehlerfrei shows what the car reports and is no substitute for a proper diagnosis.