I've just studied about the error correction schemes and encryption.
First rule when using EDC/ECC is to first encrypt and then calculate them, and the major motivation we were told is that "EDC/ECC Then Encrypt causes KPA attacks on GSM protocols to be Ciphertext Only Attacks, because it adds much redundancy to the plaintext". source (slide #50)
However I couldn't find any example or explanation for that, so I'd appreciate any help regarding this.