What happens if a module programming session fails?
Short answer: Often the module can be recovered by restarting the procedure, but sometimes it is left unresponsive and needs a recovery routine, bench programming or replacement.
Many makers design modules with a protected boot area, so if the session is interrupted the module stays in a recovery mode and accepts a fresh download. The maker's software often detects this and offers to resume or restart. Do not panic, and do not start disconnecting things.
First, check the basics: battery voltage, the pass-thru connection, the laptop's power and internet connection. Then follow the maker's recovery instructions. Some require a specific sequence of key cycles or a waiting period. Record any error codes the software shows; maker support lines may ask for them.
Prevention is better than recovery. Use a stable power supply, a dedicated laptop on AC power, a wired internet connection when possible, and a quality pass-thru. Turn off accessories, keep doors closed if the procedure says so, and never let anyone start, unplug or move the vehicle during programming. Put a sign on the car so coworkers know.
Tools used for this job
General guidance only. Follow the vehicle and tool manufacturer's procedures, and confirm vehicle coverage on the tool maker's list before buying.