I investigated and Unintended Acceleration crash that occurred on 8-9-2021. The vehicle had just left a body shop where it had repairs to the left front of the vehicle near the ECM. The driver reported the vehicle would not slow down. He face timed a witness and showed her his foot was on the brake and not the accelerator pedal collaborating his statement. The 2020 GMC accelerated to 93 miles per hour crashing into the back of a Cadillac Escalade. Upon impact the fuel tank of the Cadillac exploded igniting both vehicles on fire and burning a fed-x truck that was folded in half from the sever impact. The EDR report stated the brakes were applied fully for a full 5 seconds prior to the crash while the vehicle was still accelerating. The accelerator was reading a constant 57% during the lead up to the crash and the brake rotors showed heat related glazing from excessive braking. The engine torque was also at 1023NM leading up to impact collaborating Unintended Acceleration further. Based on the evidence gathered my opinion is there was a short in the components in the left front of the vehicle most likely the ECM harness that caused the crash. It is unknown if the damage was caused by the previous crash, the body repairs or a manufacture defect at this time. The radiator had also just been replaced so moisture could have contributed to the malfunction. If moisture shorts APP-1 to APP-2 the safety systems can fail to detect a single fault because it causes redundant faults