A system is disclosed including a primary engine that provides vehicle propulsion and a secondary engine that drives a generator to provide auxiliary power. The system further includes a first exhaust gas passageway from the primary engine and a second exhaust gas passageway from the secondary engine. The system further includes an emission treatment device including an exhaust inlet to treat exhaust from the primary and secondary engines. The system further includes an exhaust routing device that selectively routes exhaust from the first passageway or the second passageway to the exhaust inlet. The exhaust routing device at least partially blocks the first passageway or the second passageway from fluid communication with the exhaust inlet.