Understanding why an accident has occurred is going to become a whole lot more difficult. The police and their expert investigators are pretty good at diagnosing mechanical causes of accidents. They're not going to stand a chance when it comes to investigating a hack attack on a car. A good hack attack would leave no log entries anyway.
The manufacturers aren't going to want accidents investigated properly in case they are held liable for a poor design that is easy to hack in the first place. They're not interested now, and I doubt their attitude will change. [true example: A friend's car set off its own airbags whilst driving down the motorway. Despite that she was able to keep control and get off the road. Complaints to the manufacturer went utterly unanswered. Had she lost control and been killed, consider the scene that the police would find: a crashed car, airbags deployed, and a corpse. Nothing would have pointed to the true timeline of events, and it would likely have been blamed on driver error. No one knows how many times this has happened]
Which all means that drivers are going to find it very difficult to persuade either the authorities or the manufacturers or the insurers that the cause of a crash was some external hack. The driver will likely get the blame, especially if they are killed in the accident. The only way to get something done would be if hack attacks happen too many times to be ignored. By which time it will be too late for a lot of people.
On the whole I think we'd be better off without such levels of comms and automation in cars. The one that makes me laugh the most is "remote shutdown and tracking of a stolen vehicle". It's going to be easier to nick the cars in the first place via the inevitable flaws in the software. And all the thief needs is a 3G jammer to stop you tracking and stopping the car.