The word have is a stative verb. You can't convert it into the passive. "The car is being had by me" certainly wouldn't be an English sentence. On the other hand, you could say "I drove the car" or "The car was driven by me".1) I have a car.
Some stative verbs can be expressed in the passive voice. Example:
- The house is owned by Tom.
- Stative Verbs
Welcome to the forum!