Interface Arduino with a Car K-Line


im newbie in electronics i like to connect Arduino to a K-Line PIN 7 from a OBD II car plug to communicate with ECU using arduino UART.

My knowledge are:

1) The K-Line work with > 12V 2) Arduino work with 5V

This let me think that, if i connect arduino 1 RX 2 TX pins to a K-Line i will destroy the borad without a resistor :grin:

Can someone help me which has experience in electronics to create a simple circuit.

My knowledge in Electronics component are:

1) Resistors good 2) Transitor NPN PNP good 3) Capacitor good 4) Diode good 5) Opto-isolator sufficient ... .. x) Read electronics scheme sufficient :sweat_smile:

In software development i have over 15y. C/C++ experience which will not compromise this project 8)

Thanks ahead for help


Try to look for 'opengauge' or 'OBDuino' projects on google, you will find what you need. About the interface check out this

cheers, John


I quite new to adurino. I came to this interface, because it is used for ECU-Flash-read via AUD (AdvancedUserDiagnostic). I allready got a code for this AUD-reading function.

For wirting the ECU a "simpe" K-line interface is used like a FTDI-chip will be. recovery interface is a example for this:

IMO this function could be done via adurino too so I can combinate both functions or use the same interface, just flashing a other file to it ? For wirting the ECU only 5V TTL level is used AFAIK.

Did someone try to use arduino as as a simple pasthrough interface and can provide me with code for this ?

Any hints, helps etc are wellcome