No "fire code" cheat exists in The Sims 2: Pets on PSP. The PSP version is a streamlined port without the PC's cheat console or fire-starting mechanics.
SIMSLOVE — Unlock all objects/upgradesMONEY — +5,000 SimoleonsMAXMOTIVES — Fill all needsEnter these in the in-game cheat menu (accessible from pause). Using them may reduce challenge — save first!