Yes, as @ptondo said, death by exploding car is supposed to be a scripted event where the player normally dies instantly, since this doesn’t happen then you’re frozen in slow-motion. Trainers cannot alter scripted events.
What you can try doing to avoid this is to deactivate the health cheat whilst in a car and then turn it on again once you’re out of it. Otherwise, you’ll need to either reload a checkpoint or exit to the main menu and reload the game if it explodes.