Most cars will survive an EMP attack, but the vehicle that is most likely to make it through unscathed is an older diesel vehicle with minimal electronic components. To ensure your car is protected from an EMP, building a Faraday cage-type garage would be a useful project. Contrary to popular belief, an EMP attack would not disable all vehicles. According to a study conducted by the United States EMP Commission, only 1 in 50 vehicles is likely to become inoperative.
The effects of an EMP on hybrid and electric vehicles have yet to be studied and are currently unknown. This is one of the most common questions about the electromagnetic pulse, and it's important to note that there is no known mechanism by which a solar storm will destroy a car, except for making fuel unavailable due to the loss of the power grid. Even the most powerful solar storms are not known to contain the fast E1 component, which is the part of a nuclear EMP that can damage objects that are not connected to extremely long lines. The question of EMP damage to cars is so complex that it cannot be answered definitively for the reasons discussed below. The only thing on which there is a broad level of agreement among those who have studied the subject is that obtaining fuel after any type of electromagnetic disaster would be a matter of extreme difficulty.
Any particular vehicle may or may not run until it runs out of fuel; then it will no longer operate until the fuel production and distribution system can be restarted. Any statement about the effect of nuclear EMP on vehicles would depend on details such as the orientation of the vehicle (in other words, what direction it is pointing) with respect to nuclear detonation. It would also depend on the height of the detonation, the gamma ray emission from the detonation, the distance and azimuth until detonation, and the local intensity of the Earth's magnetic field between your location and the detonation point. It would also depend on whether your car is parked outside, in a concrete garage, or in a metal garage. Obviously, a metal garage is best, but concrete is slightly conductive and will provide some protection compared to being outside. However, a major problem with any ordinary garage (even an underground parking lot) is that any electrical wiring inside the garage will simply act as an EMP antenna and re-radiate the EMP inside the structure.
Over the years, several isolated vehicle tests have been carried out on EMP simulators. The car manufacturers didn't even say which cars had been tested and usually transported them to the EMP simulators in such a way that the make and model were hidden from view. So not only do we not know the result, but we don't even know what cars were tested. Discovery Channel tested a Ford Taurus on video, but it was only one particular vehicle; and questions have been raised about video editing in that segment. After having spent most of my career working for television stations and related industries, I have learned to be skeptical of television reports, regardless of their source.
The EMP Commission tested several cars and trucks at the L-3 plant in Colorado. Although this was the most complete set of tests with vehicles ever carried out, those tests were carried out very poorly because the Commission was financially responsible for the vehicles, but it did not have enough funds to pay for any of them. The vehicles were borrowed from other government agencies (most of them came from the Department of Defense); and they had to be returned to those credit agencies in good condition. Those vehicles were tested to the point that some type of fault occurred, and then further testing on that vehicle was suspended. In most cases, after the initial fault occurred, the vehicle could be restarted.
In most of the remaining cases where the vehicle could not be restarted immediately, an engagement occurred in the electronics and the battery could be temporarily disconnected to restart the electronics, and then the vehicle could be restarted. This temporary mode of electronic lock failure caused by an EMP is something that almost never happens in cars during a typical operating life. Only one of the vehicles tested (a van) could not be restarted after some minor work and had to be towed to a workshop for repair. Very few of them were tested to their maximum level on an EMP simulator. There was considerable disagreement among Commission staff members on how to report on these tests.
Some EMP Commission staff members believe that certain paragraphs in their Critical National Infrastructure Report on effects of EMPs on vehicles are quite misleading. To listen to an excellent audio conversation about these tests carried out by Auto and Truck Commission, tune into eMPact America's 41st radio program which contains a discussion between president of EMP Commission and one prominent member from their staff. In particular, debate on vehicle testing lasted approximately 46-54 minutes out of 96-minute program. It's important to note that last car model tested by USEMP Commission (as indicated in above quote) was 2002 car model.
Since 2002 number of microprocessors in cars & reliance on microprocessors in all motor vehicles has increased significantly & sensitivity of electronic circuits towards EMP has increased due to use of smaller electronic components designed to operate at lower voltages. Automakers have also conducted their own tests on EMPs. To conclude, it's difficult to predict effects of an electromagnetic pulse attack on vehicles due to wide variety & complexity involved in motor vehicles used today & lack of comprehensive testing done so far.