A vehicle bumper system comprises a bumper reinforcement beam and an energy absorber with top and bottom rows of similarly-shaped spaced-apart crush lobes in alternating relation for uniform impact resistance across the bumper system. The illustrated top row of crush lobes provides a high first force-deflection curve for high impact forces, and the bottom row of crush lobes provides a lower second force-deflection curve, for pedestrian reduced injury. An elongated sensor is positioned under shear walls of the top and bottom crush lobes, and is retained by tabs on the energy absorber. This positively retains the sensor in position on the bumper system, with few (or zero) separate fasteners, while facilitating quick assembly and reliable operation of the sensor tube.