ECU throwing EVERY fault code?

[Anarkistic]

The latest challenge I've run into on the Ph1 172 that just won't behave is the ECU.
Everything has been working fine with it up to this point, reading only a small number (less than 3 or 4) DTCs that made sense.
Changed the decat piece out for the OE cat last week, nowhere near the ECU.

Now, hook up OBD reader and bam. It's throwing what looks like every possible DTC code that exists. The only module that seems untouched is the ABS one.
Live data all works great, all sensors appear to be reading correctly. Car starts and runs (albeit a very unhappy idle, but I know why). STOP light is the only one that stays on after ignition.

What on earth has happened here?

 

[Brigsy]

The scanner you are using is not suitable. Use something that will scan it properly, can clio, renolink etc.

 

[Anarkistic]

The scanner you are using is not suitable. Use something that will scan it properly, can clio, renolink etc.

Then surely it would always have done that, no? It's a Topdon one, been doing a great job for months with that car.