I’ve got to consider this article a bit hyperbolic about the effect of an EMP. Since most cars are still made of metal, they are effectively faraday cages. A car will, after all, protect you from a direct lighting strike. So, if the electromagnetic effect of a lighting strike can be deflected, certainly a far less energetic EMP would also be deflected by the metal shell of the vehicle, leaving all the contained electronics unaffected.
Except, you car or truck has openings to the electronics: wheel wells, front grill, bottom of the car, safety glass. It’s going to be bouncing all around trying to get inside, and fry up anything electrical.