This truck was parked on a job site, on a flat parking lot over blacktop, doing a regen for the 5th time in just a few days. The truck had 4,000 miles on it. When it completed the regen, we shut the truck off. Within 15 minutes the truck was fully engulfed in flames. A fire investigator looked at it and determined the fire started in the engine bay, below the master cylinder. He said this was a GM problem. As this truck was a replacement truck, for another broken down truck, we were outside the auto coverage on our insurance. The business property is covering the tool loss, and said it isnt worth going after GM as they make it impossible. I know this isnt the only vehicle this has happened to, and they simply refuse to even answer. I want to file a formal complaint against GM, and want them to cover the loss, the loss of use. This is a safety matter as this could have happened driving down the road and caused loss of life.