Abstract: A system 10 and method for performing diagnostic testing on a mechanical safing sensor used in vehicular safety restraint and vehicle crash discrimination systems includes an accelerometer 12 having an output 14 representative of acceleration, and a processor 20 having an first input 22 responsive to the accelerometer output 14 and a second input 24 responsive to a binary output 18 generated by a mechanical safing sensor 16. The system utilizes normally occurring deceleration events to reliably diagnose safing sensor malfunctions while requiring minimal additional hardware over conventional vehicle safety restraint systems.