How many times can a vehicle be re-inspected if it fails the environmental protection test?

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If a vehicle fails the environmental protection test, it can be re-inspected twice. Below is additional information regarding environmental protection inspections: Reasons for failing the environmental protection test: Use of low-quality fuel: Frequent use of poor-quality fuel can lead to excessive carbon buildup after combustion. It may also impair the performance of exhaust purification devices, reducing their lifespan and increasing pollutant emissions, resulting in failed tailpipe emission tests. Clogged or poisoned catalytic converter: If the vehicle is frequently driven at low speeds or uses inferior fuel, the catalytic converter may become clogged or poisoned, leading to malfunction. Precautions before the environmental protection test: You can purchase professional cleaning agents to remove and clean the catalytic converter, or drive at high speeds for a certain distance. High-speed driving helps clean the engine's fuel system and cylinders effectively. Therefore, before the annual inspection, it is advisable to fill up with high-quality gasoline and drive at high speeds before undergoing the test.