From Consumer Wiki
(Civil Code § 2982 (h))
The buyer of a vehicle can obtain their own financing to purchase the vehicle, or, more typically, obtain financing through the dealer (seller). If the buyer finances the purchase through the dealer, it often tries to get one of the lenders that it does business with to make the loan. Sometimes, the dealer cannot get a lender to make the loan on the terms agreed to by the buyer in the purchase contract. In that case, the dealer may try to require the buyer to sign a new purchase contract with new terms (for example, higher monthly payments or more money down).
After the buyer has signed the original purchase contract, the seller cannot change the financing or payment terms unless the buyer agrees in writing to the change. The buyer does not have to agree to the change, and it is an unfair or deceptive practice for the dealer to make the change without the buyer's agreement. If the buyer does not agree to the change, the dealer can require the buyer to return the vehicle. The dealer may require the buyer to pay a reasonable amount for the buyer's use of the vehicle prior to returning it.
If a consumer feels that a dealer has used unfair or deceptive practices or methods, the consumer should try to resolve the complaint with the dealer. If that fails, the consumer can contact:
If a dealer does not disclose all the terms of the contract, engages in unfair or deceptive business practices, or fraud is involved in the sale of a new or used car, consumers should contact the investigative field office closest to their location.
Department of Motor Vehicles
Investigative Review Unit
PO BOX 942869
Sacramento, CA 94269-0001