[Magister]

Interesting, on my car when I shut down the engine, the ECU still answer for maybe 5 seconds before giving a timeout.

Yes in the receive function, a timeout should be inserted in the while, something like:

int iso_read_byte()
{
  byte t=0;
  int b;

  while(t!=500 && (b=serialRead())==-1)
  {
    delay(1);
    t++;
  }
  return b;
}

and the result of the function should be tested, if it's -1 it's a timeout