Car has came back to us under warranty.

New owner says eml came on and stayed on but car has shown no running problems.
Plugged in launch and found only one code.

(odf) 42 (1,f,4,20) please refer to manual.
Memory code.

Never knew what to make of this so plugged in solus to see if it gave the same code. It gave me this::

420/1056 undocumented code.

I have tried to find what these codes mean with no success. I cleared the code and all seems fine but my suspicion is it will return again?!
Can anyone shed light on this code?
Regards Brad