We present experiments which test for a nonequilibrium component to the electromotive force (emf) for a half-reaction involving species generated by a nonlinear reaction in a nonequilibrium steady state. The existence of this effect has been predicted by Keizer. The minimal bromate oscillatory reaction is run in a continuous-flow stirred tank-reactor under conditions which result in bistability. The reaction forms Ce(IV) from Ce(m) in a nonequilibrium steady state. This redox couple generates a voltage at a Pt electrode, relative to a reference electrode. Knowing the concentrations of the cerium species, this potential can be compared with that given by those concentrations of Ce(m) and Ce(IV) under equilibrium conditions, the Nernst equation. In the nonequilibrium stationary state we find deviations. We search for the source of these deviations. We do not find evidence for such explanations as mixed potentials but are unable to entirely rule them out. In the absence of such effects, the results are consistent with the existence of a non-Nernstian component of the emf for nonlinear systems in nonequilibrium steady states.