Electrorheological (ER) properties of synthesized, pristine poly(p-phenylene) (PPP) particles without any dopant treatment was investigated via flow curves including shear viscosity and yield stress. The ER characteristics were examined as functions of both particle concentration and applied electric field strengths. This undoped, PPP based suspension exhibited normal ER characteristics displayed by conventional semi-conducting polymeric ER materials with doping. The yield stress, which is an important design parameter for ER fluids, satisfied a universal scaling function. We found that the critical electric field strength for the undoped PPP suspension was much higher than the doped PPP suspension. These undoped particles can be used as a model system to test the doped system at low concentration via a universal scaling function.