L9637d is not reading

Hello Everyone,

I am trying to read k-line(ISO9141) information from my car. I found this circuit with L9637d and connected RX and TX to TTL adapter(also tried to cross them RX to TX and TX to RX). After plugging the adapter in my laptop the adapter’s blue led did not start to blink. Also I checked the serial monitor and there wasn’t anything. So I decided that maybe the chip is damaged and bought another one, but still not working.

The car is vw passat b4 '93.
the chip

I appreciate all the help!

Thank you!



Before using the TTL adapter I tried to read the data with Arduino. I am trying to make something like Trip computer for measuring the battery voltage temperature of the cooling system and other stuff.


I there is some other way or idea to read K-line I am glad to head it.

I am using this code for arduino

#include <SoftwareSerial.h>

SoftwareSerial mySerial(10, 11); // RX, TX

void setup() {

  while (!Serial)

void loop()
  if (mySerial.available())

I want to read my car ECU coolant Temp. with using this circuit , please help me to write program .


Anyone can give a code solution to read k line of injection motorcycle using the L9637D circuit? thank you