Custom Firmware for PSP 5.51? None Exists

No CFW for 5.51. Sony patched the kernel exploit used by 5.00 M33 / 5.50 GEN. No new exploit was ever released for 5.51.

Options

• Downgrade to 5.00 / 5.50 — Requires Pandora Battery + Magic Memory Stick (hardware mod). Works on 1000/2000/3000 (non-TA-088v3).
• 6.60/6.61 LME / PRO-C2 — If you can update to 6.60/6.61 (official), these temporary CFW (FastRecovery) install in seconds, no Pandora needed. Best path today.
• Homebrew Enabler (HEN) — Limited; no ISO loading, only signed homebrew.

Recommendation

Update to 6.61 → Install PRO-C2 FastRecovery → Enjoy ISOs, plugins, emulators. Re-run FastRecovery after each cold boot.

⚠️ CFW voids warranty (irrelevant now) and can brick if done wrong. Follow wololo.net or PSP-Hacks guides exactly.