Version 1.21 significantly enhanced existing packages for broader vehicle coverage: Added Hitachi SH725x3 support.

| Feature | Pcmflash 1.21 | Kess V2 (Clone) | Autotuner (Original) | | :--- | :--- | :--- | :--- | | | $50 - $120 (clone) | $100 - $200 | $4,000+ | | Subscription | None | None (clones) | $1,000/year | | Boot Mode | Yes (manual wiring) | No | Yes (automatic) | | Checksum | Auto | Auto | Auto | | New ECU Support (2020+) | No | Limited | Yes | | Learning Curve | Moderate | Low | Moderate |

PCMflash 1.21: Comprehensive Guide to the 2020 ECU/TCU Tuning Update

Regular updates via the official PCMflash website , which includes updated diagrams.

Allows reading the full flash and EEPROM on supported modules, enabling total ECU cloning.

If you intend to tune the ECU, open the read file in a tuning tool such as WinOLS, make your changes (e.g., adjust fuel maps, timing, boost limits), and save the modified file.

The most common error when writing modified files is a "checksum mismatch". The ECU constantly checks its own code for integrity. If the checksum doesn't match, the vehicle will go into limp mode or fail to start. Pcmflash 1.21 includes an feature that recalculates and corrects these values before writing, saving hours of manual hex editing.

Pcmflash 1.21 Jun 2026

Version 1.21 significantly enhanced existing packages for broader vehicle coverage: Added Hitachi SH725x3 support.

| Feature | Pcmflash 1.21 | Kess V2 (Clone) | Autotuner (Original) | | :--- | :--- | :--- | :--- | | | $50 - $120 (clone) | $100 - $200 | $4,000+ | | Subscription | None | None (clones) | $1,000/year | | Boot Mode | Yes (manual wiring) | No | Yes (automatic) | | Checksum | Auto | Auto | Auto | | New ECU Support (2020+) | No | Limited | Yes | | Learning Curve | Moderate | Low | Moderate | Pcmflash 1.21

PCMflash 1.21: Comprehensive Guide to the 2020 ECU/TCU Tuning Update Version 1

Regular updates via the official PCMflash website , which includes updated diagrams. If you intend to tune the ECU, open

Allows reading the full flash and EEPROM on supported modules, enabling total ECU cloning.

If you intend to tune the ECU, open the read file in a tuning tool such as WinOLS, make your changes (e.g., adjust fuel maps, timing, boost limits), and save the modified file.

The most common error when writing modified files is a "checksum mismatch". The ECU constantly checks its own code for integrity. If the checksum doesn't match, the vehicle will go into limp mode or fail to start. Pcmflash 1.21 includes an feature that recalculates and corrects these values before writing, saving hours of manual hex editing.