This light commonly flashes when there are transmission issues. Have you noticed any performance issues? The idea that you notice it at high speeds and at an idle leads me to think there could be an issue with the TCC (torque converter clutch solenoid).
If you haven't, I would start by scanning the can-bus system. CAN stands for controller area network. All modules/computers are tied together via a few wires. This should indicate if there is a code stored, regardless of the module holding it.
Take a look through this link. It explains the procedure and how it works.
Let me know if you have already done this. Also, if codes were found, let me know.
Monday, December 6th, 2021 AT 6:49 PM