For Spain’s mandatory Inspección Técnica de Vehículos (ITV), emissions are one area that can catch drivers out. Figures attributed to AECA-ITV put the 2025 pass rate at 81%; the reported share of failures approaching one quarter combines defects in lighting and signaling, with emissions also among the causes. For many drivers, preparation, including bringing the engine to normal operating temperature, can help avoid an unrepresentative test, says mechanic Juan José.
“If you want to avoid a negative result for emissions, you need to bring your car in hot,” Juan José advises. Spain’s ITV emissions checks follow a national inspection structure, not an optional practice set by individual stations. The test differs by engine type: diesel vehicles are checked for exhaust-gas opacity, an indicator of particulate smoke, while spark-ignition vehicles are assessed for pollutants including carbon monoxide. Where applicable, inspectors also use the onboard diagnostic system (OBD) to check for emissions-related warning indicators and recorded faults. These are distinct checks: warming the engine may help emissions-control equipment operate under representative conditions, but it does not erase a stored fault or repair a malfunction.
Juan José warns against arriving with a car that has just been started or driven only through slow city traffic. Catalytic converters and diesel particulate filters rely on elevated exhaust temperatures to convert pollutants or remove particulates, and a short urban journey may not bring them to normal operating conditions. “It’s common to see cars fail the test when, in reality, there’s nothing wrong with them,” he explains. “You don’t need to lead aggressively,” he clarifies, “but the car should be at operating temperature.” A lead long enough to warm the vehicle can make the measurement more representative. Aggressive revving is no substitute for maintenance or repair, and drivers should follow the inspection station’s instructions.
High diesel opacity can be associated with poor combustion or faults affecting intake or injection, the turbocharger, or exhaust after-treatment. Elevated carbon monoxide in a petrol vehicle can point to incomplete combustion or an air-fuel-control problem. If a vehicle fails repeatedly, produces visible smoke, shows an emissions warning light or records abnormal diagnostic readings, it needs professional diagnosis. A warm engine can improve test conditions, but it cannot correct a genuine mechanical or emissions-system defect.
This practical preparation can save drivers time and money, but regular servicing remains the best defense against ITV surprises. Keeping the engine and emissions-control equipment in good condition, including the exhaust, improves the chance of meeting the applicable limits and helps preserve the vehicle. If an ITV result is unfavorable, the defect normally needs to be repaired and the vehicle returned for a follow-up inspection under the applicable regional and station procedures.
Emissions standards and testing procedures have become stricter in recent years, reflecting broader efforts to reduce air pollution and improve public health. Electric and hybrid vehicles are subject to inspection criteria that differ from those for conventional combustion-engine cars. For a look at how new technologies are shaping the automotive field, see this comparison of four standout electric SUVs that are redefining everyday driving in Spain.
As the ITV continues to evolve, small details, like arriving with a warm engine, can affect test conditions. For Spanish motorists, preparation and routine maintenance are sensible ways to reduce the risk of an avoidable setback at inspection time.
