Will not start, has no RPMs?

So, does it have spark or no? If you have a shorted ignition coil it will shut down the coil driver inside the PCM. I would unplug all ignition coils and install one brand one coil to see if it sparks when cranking the engine over. Also, the code gathering that has done has it a CAN scan? This kind of scan does the entire car including the BCM and is more helpful than an engine code scan. You can get a CAN scanner (Controller Area Network) from Amazon from about $32.00.

Here is a video to show you how:

https://youtu.be/u-4syLc-ifQ

and

https://www.2carpros.com/articles/can-scan-controller-area-network-easy

Amazon CAN scanner Link.

https://amzn.to/3G7mpFP

Also, they didn't make a Lesabre in 2020 can you please double check the year? Check out the images (below). Let us know what happens and please upload pictures or videos of the problem.