| Error Code | Meaning | Exclusive Fix | | :--- | :--- | :--- | | | Checksum mismatch | Re-flash using parallel port (not USB). The exclusive package includes a legacy LPT flasher. | | Continuous paper jam | Sensor timing changed | Open the rear output door. The exclusive firmware recalibrates sensor thresholds after 10 open/close cycles. | | “Unsupported cartridge” after update | Region lock engaged | Enter service mode (Press Go 5x after power-on). Send raw ESC code ESC&+3E to override. |
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The exclusive firmware includes a "Toner Density Adjustment" for non-HP cartridges. Navigate to Service → Calibrate → TD Adjust . Set to -2 to improve yield on generic 49X cartridges by up to 18%. hp lj 1320 firmware update exclusive