At the main menu, press L1(2), R1(2), L2(2), R2(2). If you entered the code correctly, you will hear the sound of a burp. Then, begin a race in endurance mode. Press Triangle to be flown to the next checkpoint by helicopter.
Drive ice cream truck
At the truck selection screen, hold L1 + R2 while selecting the driver of the van.
Increased traction
At the main menu, press Left, L1, R2, R1, Left, R2(3). If you entered the code correctly, you will hear the sound of a burp.
Monster trucks
At the main menu, press L1, R2, L2, R1, Up. If you entered the code correctly, you will hear the sound of a burp.
No damage
At the main menu, press Left(4), Up, Down, L1, R2. If you entered the code correctly, you will hear the sound of a burp.
Super vehicle
At the main menu, press L2, Left, Right, Up, Down, R2. If you entered the code correctly, you will hear the sound of a burp. Now the durability of all trucks will increase.