: A battery maintainer is critical during writing to prevent voltage drops that could "brick" (permanently damage) the ECU. Getting Started Guide Downloads - PCMflash

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

: Coverage for various Chevrolet and Ford powertrain modules. ⚠️ Important Considerations : A battery maintainer is critical during writing