Oil leakage is a common fault in commercial MR damper. The monitoring of the suspension transmissibility, magnitude ratio between the sprung and unsprung mass accelerations, allows to detect a fault in a damper. Two proposed approaches: Force sensor based (FT R ) and Accelerometers sensor based (AT R ) online estimate the suspension transmissibility. The concept is validated in a vertical model of a single vehicle. Using a Receiver Operating Characteristic (ROC) curves, the best threshold is defined. Early results have less than 26 % average in detection error for AT R approach, which is a 9 % better than FT R approach. Intensive validation in a full vehicle model in CarSim" shows the feasibility of practical implementation of this fault detection system. © 2012 IFAC.