Emissions over the limit
How it can appear on an MOT certificate
- “Exhaust emissions exceed the manufacturer's specified limits”
- “Emissions over the default limits”
What it is
The MOT measures the gases from the exhaust (or, for diesels, smoke opacity) and compares them with the limits for that car.
Why it matters
High emissions are bad for air quality and can point to a fault such as a failing catalytic converter, a sensor problem or poor running.
What to check when viewing a car
Ask whether the cause was found and fixed. Check the engine starts and idles smoothly with no warning lights.
Has the car you're looking at had this before?
Free: every MOT, every defect explained in plain English, mileage, tax and ULEZ.
What the MOT categories mean
- Dangerous
- A direct and immediate risk to road safety, or a serious impact on the environment. The car fails and shouldn't be driven until it's repaired.
- Major
- It may affect the car's safety, put other road users at risk or harm the environment. The car fails and should be repaired straight away.
- Minor
- No significant effect on safety or the environment. The car passes, but it should be repaired as soon as possible.
- Advisory
- Something to keep an eye on that could need repairing in future. The car passes.
Related: exhaust and emissions
- Exhaust leak
- Exhaust insecure or mountings damaged
- Diesel smoke over the limit
- Engine warning light (MIL) on
- Catalytic converter missing or not working
Buying a used car?
General information about this type of MOT defect, not advice about a particular car. How serious it is depends on the car; have any car you're buying inspected by a qualified mechanic.