| 摘要 |
A system and method for detecting tampering with a vehicle speed sensor input signal include determining a current gear ratio, comparing the current gear ratio to at least one reference gear ratio to determine a gear ratio difference value, and generating an error signal indicating tampering with the vehicle speed sensor signal when the gear ratio difference value exceeds a first threshold. In one embodiment the step of generating an error signal is performed only when the gear ratio difference value exceeds the first threshold for an elapsed time greater than a predetermined time period. One embodiment includes determining a current engine speed, current vehicle speed, and current transmission gear ratio and storing values for the current engine speed, vehicle speed, and transmission gear ratio in the memory whenever at least one predetermined criterion is satisfied. The system and method calculate difference values between the current engine speed, vehicle speed, and transmission gear ratio and corresponding previously stored respective values. A signal indicating tampering is generated when at least one of the difference values exceeds a corresponding threshold.
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