A powertrain system includes a torque machine rotatably coupled to an internal combustion engine via a pulley mechanism. The torque machine and the internal combustion engine are configured to transfer torque to a driveline and include a first sensor configured to monitor rotation of the engine and a second sensor configured to monitor rotation of the torque machine. The first sensor signally connects to a controller configured to control operation of the torque machine. A method for operating the powertrain system includes employing a signal output from the first sensor to monitor rotation of the torque machine to control operation thereof, said signal output from the first sensor adjusted for a pulley ratio of the pulley mechanism upon detecting a fault associated with the second sensor.