I got it working right away without modifications. I had to modify it as once the car turned off, I would have to reset the arduino to reinit, which is impractical to do...
Have you verified the chip functions?
With a volt meter you should see the K line high, and drop down to zero volts. Powered by the computers USB, high will only be 5 volts, but that's ok. It will tell you the car will get 12 volts once it's hooked up to the car.
That tells you the TX is working. Next, add some code to the iso_init to read back the RX line. Before you change the K line state (HIGH or LOW) read the K_in line with digitalRead(k_in); do the same after, and the results should differ. If not, you won't hear the car. So check that wiring.
If all the wiring is good, and the chip is working, then your car is either expecting something else before it talks to you, or, you are ignoring what it says.
Try checking for ANY feedback from the car. Change the code to be successful if the car sends any data at all back. See if you still time out or not. If you still time out, then the car is still waiting for what it thinks is the correct startup sequence (whatever that is).