I’ve had both a Toyota and a Honda recalled for software issues, and I’ve seen the actual recall notices for both. For the Toyota (a hybrid) the recall notice and a letter came in the mail explaining that I’d get a usb stick in the mail. A few weeks later I got it along with instructions on how to install it. It basically said to plug it into the car, turn the car on, then wait about 10 minutes until you saw a certain message.

The Honda was a huge pain. For a few years I would find the battery was dead after a long drive. It was very intermittent. Three mechanics and 2 batteries later it was still happening. Dealer mechanics were no help either. Eventually I posted the symptoms on a Honda enthusiasts forum, and within a few days I was pointed to two different recall notices that described my problem perfectly. They were software bugs in the ECU that would cause the alternator to be disabled occasionally when it shouldn’t. The only problem is the range of VINs on those recalls didn’t match my car.

I took printouts of the recalls to a dealer, they checked and confirmed my car had the buggy ECU software. They updated it, and I never had that problem again.