Under what condition should the odometer or speedometer fail inspection?

The odometer or speedometer will fail inspection if they are not registering distance or speed. This is critical because these instruments play essential roles in monitoring vehicle performance, ensuring compliance with speed limits, and helping drivers understand how far the vehicle has traveled. Accurate readings from the speedometer are necessary for safe driving, as they allow drivers to adhere to traffic regulations. Similarly, the odometer is important for maintenance schedules and tracking vehicle wear and tear.

In contrast, illumination issues, noise, and the digital nature of the instruments do not directly affect their fundamental function of providing accurate speed and distance readings. Speedometers that do not illuminate can still provide accurate readings, and digital speedometers, as long as they function correctly, are acceptable. Noise does not typically lead to a failure either unless it indicates a malfunction affecting performance. Thus, the failure to register distance or speed directly impacts the vehicle's safety and operational compliance.