how can I correct division by zero error in a simulik model

in a vehicle model and when runing it appear a messsage text which is " Algebraic state in algebraic loop containing '........../Product33' computed at time 0 is Inf or NaN. There may be a singularity in the solution. If the model is correct, try reducing the step size (either by reducing the fixed step size or by tightening the error tolerances).in an other and on the command window I found warning:Division by zero in Product6' and another Warning: Division by zero in Product22'. please help me to solve this problem,I'll be grateful.thanks.