In this section
8.2.1. Spark ignition engine emissions
8.2.1.1. Exhaust emission control equipment
You only need to check components that are visible and identifiable, such as catalytic converters, oxygen sensors, and exhaust gas recirculation valves.
You should reject all vehicles first used on or after 1 September 2002, where original emissions control equipment components are missing, obviously modified or obviously defective.
Vehicles used prior to 1 September 2002 should only be rejected, where a full catalyst test could apply. Use the flowcharts 1, 2 and 3 to decide which emission test is applicable for the vehicle being tested.
| Defect | Category |
| (a) Emission control equipment fitted by the manufacturer: missing, obviously modified or obviously defective | Major |
| (b) An induction or exhaust leak that could affect emissions levels | Major |
8.2.1.2. Gaseous emissions
Engine malfunction indicator lamp (engine management light or EML)
Turn on the ignition and check that the engine malfunction indicator lamp (MIL) illuminates and then goes off. On some vehicles it will be necessary to start the engine before the MIL goes off.
You need to inspect MIL fitted to:
- petrol vehicles including hybrids with 4 or more wheels, not more than 8 passenger seats in addition to the drivers seat and first used on or after 1 July 2003
- petrol vehicles including hybrids with 4 or more wheels, more than 8 passenger seats in addition to the drivers seat and first used on or after 1 July 2008
- gas and bi-fuel vehicles including hybrids with 4 or more wheels, not more than 8 passenger seats in addition to the drivers seat and first used on or after 1 July 2008
Kit cars, amateur built vehicles and American pickups are not required to be fitted with an engine MIL.
Visual inspection (all vehicles):
Raise the engine speed to around 2500rpm or half the maximum engine speed if this is lower. Hold the engine speed steady for approximately 20 seconds and allow the engine to return to its natural idle speed.
Once the idle speed has stabilised assess the smoke emitted from the tailpipe. If the exhaust is emitting dense blue or clearly visible black smoke then the vehicle will fail the test.
In exceptional cases, especially on certain vehicles manufactured before 1960 where emissions of smoke are unavoidable due to the engine design, these vehicles will not fail the test.
Vehicles with two stroke engines also emit smoke that is not avoidable and should not be failed unless the exhaust emits excessive dense blue or clearly visible black smoke during acceleration which would obscure the view of other road users.
This test may be done in conjunction with the check of the vehicles noise suppression system Section 8.1.1
Emissions testing
You must inspect vehicles with spark ignition engines first used on or after 1 August 1975.
You do not need to check:
- L category vehicles
- hybrid vehicles - with electric and combustion engines
- hydrogen fuel cell vehicles
- two-stroke engines - unless they are subject to a catalyst test
If an engine has been modified in any way, it still must meet the exhaust emission requirements according to the age of the vehicle.
For emissions purposes only you should treat the following as first used before 1 August 1975:
- kit cars and amateur-built vehicles first used before 1 August 1998
- Wankel rotary-engined vehicles first used before 1 August 1987
- Q plated vehicles
To prevent the build-up of fumes, the test should be carried out in a well-ventilated area.
Personal imports
A personal import must be tested according to its date of first use. However, if youre shown a letter from the vehicle manufacturer proving that the engine does not meet British emission standards you must test to the next lower emission standard.
For example, a 1995 car first used in Gambia with a letter from the engine manufacturer stating the engine number and showing that the engine cannot meet catalyst emission limits, you must use the non-cat limits of carbon monoxide (CO) 3.5% and hydrocarbons (HC) 1,200ppm.
Vehicles fitted with a different engine
If a vehicle first used before 1 September 2002 is fitted with an engine thats older than the vehicle, you must test it to the standards applicable for the engine. The vehicle presenter must have proof of the age of the engine.
If a vehicle first used on or after 1 September 2002 is fitted with a different engine, you must test it to the emissions standards for the age of the vehicle.
For emission standards on kit cars, read further.
Kit cars
Kit cars and amateur-built vehicles first used on or after 1 August 1998 must have either Single Vehicle Approval (SVA) or Individual Vehicle Approval (IVA).
You must test kit cars or amateur built vehicles to the limits in the vehicles registration document (V5c). If the V5c does not show any limits, you must test it to the limits of the engine fitted at the time of the SVA or IVA test.
Vehicles exempt from emission limits
Some vehicles may never have been able to meet the MOT limits for CO or HC emissions. The vehicle owner must provide proof of this, such as a letter from the vehicle manufacturer. If the vehicle owner cannot provide proof of this, you must fail the MOT test if the vehicle is not within the emissions limits.
Passenger cars
A passenger car is a vehicle that:
- is constructed or adapted to carry passengers
- has up to 5 passenger seats, excluding the drivers seat
- has a DGW not exceeding 2,500kg
- is not a goods vehicle, such as a pick-up or a car-derived van
If youre not sure if a vehicle is a passenger car, you can confirm it by:
- getting the DGW from the manufacturers VIN plate
- checking if the vehicle is listed in section 2 of the current emissions data book
- checking the owners handbook or a data book
If you cannot find proof that the vehicle is a passenger car, you must assume its not a passenger car.
Specialist conversions
For emissions purposes, you must treat specialist conversions as if they had not been converted.
For example, a motor caravan or ambulance converted from a
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