I understand the general concept of desensitization/counterconditioning for dogs when it comes to dog training. I want to expose him to the car in very gradual bouts before he reaches his threshold, and create positive associations with the car. Let him sniff around the car, open the door to let him explore, get in the car without going for a ride, give him treats in the car, etc. letting him experience the car in ways he is comfortable with, it at his level, and before he reaches a threshold of anxiety, fear, etc.

I'm also told though that I need to limit or prevent his exposure to the thing he is afraid of but I'm not really sure how to do that with the car. There are times he needs to come with us and when he does, he reacts to the car the way he always does. He shivers uncontrollably, passes his threshold, and wont accept food, listen, etc.

Is the desensitizing process helping if he is still getting in the car, in between training? Are there ways to deal with this and still effectively teach him that he doesn't need to fear the car?