This communication reports, for first time, how the simultaneous record of the solution potential and sonocurrent transient on a working electrode at fixed potential can provide meaningful information on the oscillatory mechanism for oscillating reactions driven in a highly passivated environment. The advantages of ultrasonically enhanced chronoamperometric analysis in comparison to potentiometry were tested. Those techniques were used for the study of the effect of isobutylmethyl ketone on the uncatalyzed class of bromate oscillating chemical reaction (UBO). This communication presents experimental results that support the hypothesis that methyl ketones consume the molecular bromine that is formed during the UBO reaction.