The Consonant-Vowel hypothesis suggests that consonants and vowels tend to be used differently during language processing. In this study we explored whether these functional differences trigger different neural responses in a rule learning task. We recorded ERPs while nonsense words were presented in an Oddball paradigm. An ABB rule was implemented either over the consonants (Consonant condition) or over the vowels (Vowel condition) composing standard words. Deviant stimuli were composed by novel phonemes. Deviants could either implement the same ABB rule as standards (Phoneme deviants) or implement a different ABA rule (Rule deviants). We observed shared early components (P1 and MMN) for both types of deviants across both conditions. We also observed differences across conditions around 400 ms. In the Consonant condition, Phoneme deviants triggered a posterior negativity. In the Vowel condition, Rule deviants triggered an anterior negativity. Such responses demonstrate different neural responses after the violation of abstract rules over distinct phonetic categories.