The vehicle was driven to a job site in Gowanda NY. The computer indicated it neede to clean the exhaust filter. The truck was parked in an open area on a blacktop parking area. The truck finished a Regen approximately 30 minutes later. The vehicle was shut down and left unattended. Approx 30 minutes later, the driver, heard noises, came around a structure and saw the vehicle was on fire. The driver did attempt to use a fire extinguisher to no avail. They then called 911 and the fire department was dispatched. The department put out the fire but the vehicle is a total loss. As this was a work site, the vehicle was towed to our shop and stored inside. The inland marine insurance company hired a fire investigator, and they looked at the vehicle. They determined the fire originated on the lower firewall in the engine compartment. He paused his investigation, to await a representative of GM to be present for destructive analysis to determine exact cause. The GM case number is XXX. This vehicle had errored multiple times and did Regen every 2-300 miles. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)