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• Could my car fail MOT for emissions?
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Could my car fail MOT for emissions?

Yes, your car can fail its MOT if it doesn’t meet the legal emissions standards for its fuel type and age.

During the test, your car’s exhaust emissions are measured to ensure it’s not producing excessive pollutants.

For petrol cars, this includes checks on carbon monoxide (CO), hydrocarbons (HC), and the lambda reading.

For diesel vehicles, the test looks for visible smoke and checks the Diesel Particulate Filter (DPF) if fitted.

Common reasons for failing include:

• A damaged or missing DPF (diesel only)
• Faulty sensors (like oxygen or mass airflow sensors)
• Dirty air filters or worn spark plugs
• A lit engine warning light
• Black or blue smoke from the exhaust

To reduce the risk of failure, keep your car well maintained, avoid short trips (especially in diesels), and make sure the engine is warmed up before the test.

Read our compehensive guide on MOT emissions failure for an extended breakdown on what emissions means for your MOT test and how to deal with a failed emissions test.