In a vehicle from 2001 or newer, how many monitors must be on for the vehicle to fail inspection?

For vehicles from 2001 or newer, the inspection guidelines specify that if two or more monitors are found to be inoperative or "not ready," the vehicle will fail the inspection. This requirement is based on the need for the on-board diagnostics systems to be fully operational in order to ensure that the vehicle meets emissions standards and operates safely.

When a vehicle's monitors are run through their testing cycles, they check various systems for proper functionality, including emissions control, fuel system, and exhaust systems. If two monitors are not ready, it indicates a potential problem with these critical systems, thus justifying a failure in the inspection process.

In this case, having one monitor not ready would not warrant failure, as the vehicle could still potentially meet safety and emissions standards, provided other monitors are operational. Similarly, having three or four monitors not ready indicates an increasing concern, but the critical threshold for inspection failure is established at two monitors. This helps to ensure that only vehicles with significant diagnostic issues are flagged for failing the inspection.