Engine light, reduced power, service ecu, service parking break

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Hi all just had an issue with truck. I was parked idling I had shut off traction control put the truck into drive the second I pressed the gas pedal the dash lit up. Reduced power, service parking break, service ecu. I shut it down and let it sit for a couple minutes. Started it back up Everything cleared but the engine light stayed on. Any thoughts ?? . 2020 custom trail boss with the 5.3 tried checking codes with a elm reader that has worked in the truck but now it wont