Detection of faults in an injector arrangement

A fault detection method for detecting short circuit faults in an injector arrangement at engine start-up. The injector arrangement comprises one or more piezoelectric fuel injectors (12a, 12b), which are connected in a drive circuit (20). The potential (VB) at a bias point (PB) in the drive circuit (20) is determined and compared with a predicted voltage (VPB). A short circuit fault signal is generated if the potential (VB) at the bias point (PB) is not within a predetermined tolerance voltage (VTOL) of the predicted voltage (VPB).