Hi, ECC cannot be disabled and it is always enabled.
The only difference is in the suppressed error reporting on data flash with MPC57xx as described here, section 2.4.2:
https://community.nxp.com/docs/DOC-339955
However this way it works only with data flash, not code flash. In case code flash, reading or execution of data field affected by multi-bit ECC error causes bus error.