For remanufacturing automobile subsystems, the knowledge of future failure rates of systems produced in serial production is from great importance. Remanufacturing departments especially need information about the number of cores to remanufacture, the condition of those cores as well as the number of replacement system the market requires. On the basis of an already existing model that predicts failure rates using warranty data as input, a bivariate prognosis model is developed, which takes two variables of stress in field into account. By enhancing the existing model a more precise prognosis of future failure rates is expected as well as a better knowledge of the damage. This paper presents all necessary mathematical tools to perform a bivariate lifetime prognosis as well as the implementation in MATLAB.