Low cost OBD2 communications on K-line

Cheap OBD2 communications on K-line

This is just another OBD2 solution for monitoring the sensors in a verhicle. It supports the K-line OBD2 serial communication between a verhicle and a microcontroller. This K-line communication is also known as ISO 9141-2 or ISO 14230-4 (also known as Keyword Protocol 2000 or KWP). Both ISO’s are almost similar. This solution differs from the rest that is low cost (for less than 10 euro!!). It is low cost in the way that you don’t need an arduino, raspberry pi or smart phone. Just a microcontroller and LCD display so you can use your smartphone for other purposes.

Main features:

  • Shows verhicle engine load, temperature, speed and RPM on a LCD display
  • Optically displaying the engine load via a LED by changing the intensity using the microcontroller PWM module
  • When temperature exceeds 93 degrees a buzzer will be triggered
  • A watchdog will quard communication problems between microcontroller and verhicle ECU

To do:

  • Display stored diagnostic trouble codes in mode 0x03 (routine is included but I have to wait till my car gets troubles)
  • Clear trouble codes / Malfunction indicator lamp (MIL) / Check engine light (routine is included but untested)
  • Support “fast init”

It is tested with a Citroen C1 gasoline (2013) and VW Touran gasoline (2003). Probably it will work for a Peugeot 107 and Toyota Aygo of 2013 as well since they are technically identical. From what I read on the internet there are many flavours on K-line around so there is a possibility it will not suit your car. Maybe some changes are needed to make it work. The source code is provided so you can investigate and change when needed. Maybe you can help extending this list of cars to help others!

1 x LM7805 1A regulator

1 x 330nF ceramic capacitor

1 x 100nF ceramic capacitor

1 x 510 Ohm resistor

1 x 2.2K Ohm resistor

1 x 47K Ohm resistor

1 x 33K Ohm resistor

1 x 100 Ohm resistor, optional (for blue led, please use appropriate resistor for other colors)

1 x LED, optional

2 x 10K Ohm trim resistor

1 x Buzzer 5 volt (< 20mA), optional

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