California Lemon Law requires a new car to be replaced or refunded if it spent more than 30 days in service, or had four warranty repairs for the same problem, or two repairs if the problem was safety-threatening. Lemon Law applies only during first 18 months or 18,000 miles.
I'm not a lawyer, researched this for myself and found that the text of the provision seems to be confusing on purpose. I put together what I learned in plain language, for my own record.
Every new car sold in California is sold with manufacturer's warranty by default. The Song-Beverly Consumer Warranty Act says a new car must be replaced or refunded if it doesn't comply with the warranty after a reasonable number of repair attempts. The Lemon Law specifies what is the reasonable number, and also what is a new car and how the matter is settled. The Lemon Law applies to personal cars and cars belonging to small businesses.
A new car is a car sold with the manufacturer's warranty. It includes the demo cars and the cars with any portion of the three-year warranty left, but not used cars older than that. The "car" includes the chassis and cab of an RV but doesn't include the living part of the RV, or any cargo cars, motorcycles or off-road vehicles. The Lemon Law doesn't apply to after-market parts and to abused cars.
The Lemon Law applies to the first 18 month or 18,000 miles, whichever comes first, after purchase. The reasonable amount of repair attempts is four for the same problem, or two is the problem is life- or safety-threatening. Lemon Law also applies if the car was in repair for more then 30 days during this period (not in a row, necessarily), for any number of warranty problems. The Lemon Law criteria are only guidelines. If the criteria are met (and documented), the buyer can go to the court, or arbitration first. Car dealers usually participate in state-certified arbitration programs. Arbitration is cheaper and simpler than going to the court, and the buyer has the right to reject the arbiter's decision and sue the manufacturer or the dealer.
Again, these are my notes to myself and they might or might not be useful for anyone else. Plenty of lemon law lawyers provide advice on lemon law, and most give a free initial consultation. Some even work on contingency (meaning they only get paid if and when they win). My notes are my opinion only.