MOT fail · manual section 8.2.1.2

Petrol exhaust carbon monoxide content after 2nd fast idle exceeds manufacturer's specified limits

What this MOT fail means, how often testers record it and what the usual repair costs. From 130,233,413 DVSA MOT tests taken 2022 to 2025.

MOT data updated 28 September 2026

As a fail, per 100 MOTs (n=130,233,413)0.20

Most often at25 years

Times recorded265,339

Times recorded adds every DVSA code with this wording, so a test can record it more than once, for example on two wheels under separate codes.

What it means

This is a major defect: the car fails its MOT. A major defect may affect the car’s safety, put other road users at risk or harm the environment. The car fails its MOT and the defect must be repaired.

Exhaust emissions are measured against limits for the car’s age and fuel, and the car is checked for fluid leaks and excessive noise.

The MOT inspection manual describes the defect (section 8.2.1.2) as:

Emissions levels exceed the manufacturer's specified limits

Read this section of the MOT inspection manual on GOV.UK

The DVSA codes counted on this page: the manual item and the defect text as DVSA records them. The heading above joins the two, as a certificate does; the tester also adds the position, such as nearside front.
Result	Manual item	DVSA defect text	Records
Fail Major	Catalyst emissions	carbon monoxide content after 2nd fast idle exceeds manufacturer's specified limits (8.2.1.2)	265,339

Got an MOT advisory or defect on a certificate? Paste it into the MOT advisory checker to see what it means.

How common it is by age

Testers record it most at 25 years: 1.69 per 100 MOTs (n=313,355 tests at that age).

Per 100 MOT tests of cars at each age, all makes. We show no figure below 20 tests.
Age	Fail per 100	Tests (n)
3 years	0.011	8,016,463
4 years	0.022	8,699,937
5 years	0.035	9,425,360
6 years	0.055	10,382,720
7 years	0.078	10,537,318
8 years	0.10	10,440,457
9 years	0.12	9,949,012
10 years	0.14	9,049,507
11 years	0.16	8,087,514
12 years	0.18	7,303,151
13 years	0.23	6,612,160
14 years	0.31	6,054,526
15 years	0.41	5,591,675
16 years	0.48	4,858,625
17 years	0.52	4,040,458
18 years	0.56	3,261,622
19 years	0.62	2,479,858
20 years	0.69	1,845,952
21 years	0.77	1,321,417
22 years	0.97	913,980
23 years	1.18	619,531
24 years	1.43	428,815
25 years	1.69	313,355

Models that get it most

Each model generation is compared with cars of the same ages and fuel, so older and diesel models are not penalised for their age or fuel. Generations are never pooled.

Model generations with the highest rate as a fail, against cars of the same ages and fuel. A model’s figure counts this defect only at ages where it is among that model’s 25 most recorded items, and as zero elsewhere, so it is a floor. Tests (n) are all the generation’s MOT tests at ages with at least 1,000 tests each; at least 5,000 in total.
Model	Per 100 MOTs, at least	Same ages and fuel	Times as often	Tests (n)	Ages
Peugeot 208Peugeot 208 emissions fail repair Peugeot 208 exhaust and emissions problems	0.90	0.15	6.0	809,087	3 to 13
Hyundai Tucsonfirst used 2015 or laterHyundai Tucson exhaust and emissions problems	0.21	0.040	5.1	520,466	3 to 10
Mazda RX-8Mazda RX-8 exhaust and emissions problems	3.31	0.83	3.9	9,840	15 to 19
MG ZSfirst used 2017 or later	0.14	0.039	3.6	143,170	3 to 7
Peugeot 2008Peugeot 2008 emissions fail repair Peugeot 2008 exhaust and emissions problems	0.26	0.073	3.6	496,383	3 to 12
Kia Sportage	0.17	0.053	3.1	1,070,582	3 to 19
Peugeot 308	0.30	0.10	2.9	549,521	3 to 17
Mazda Bongo	1.27	0.44	2.8	35,066	6 to 25
Nissan 350ZNissan 350Z exhaust and emissions problems	2.34	0.90	2.6	18,548	15 to 21
Peugeot 106Peugeot 106 exhaust and emissions problems	3.53	1.35	2.6	16,165	20 to 25
MINI Cooper and OneMINI Cooper and One emissions fail repair	0.84	0.33	2.5	2,619,239	3 to 24
Peugeot 306Peugeot 306 exhaust and emissions problems	2.42	1.03	2.3	14,057	21 to 25
Volkswagen BeetleVolkswagen Beetle emissions fail repair Volkswagen Beetle exhaust and emissions problems	1.21	0.52	2.3	180,577	5 to 24
Subaru ImprezaSubaru Impreza emissions fail repair Subaru Impreza exhaust and emissions problems	2.34	1.02	2.2	66,952	12 to 25
MG MGFMG MGF exhaust and emissions problems	3.85	1.71	2.2	17,499	21 to 25
Citroen SaxoCitroen Saxo exhaust and emissions problems	2.81	1.28	2.1	14,904	19 to 24
Honda HR-Vfirst used before 2015	2.56	1.25	2.0	5,740	20 to 23
Ford Escort	2.21	1.09	2.0	6,428	22 to 25
Volkswagen LupoVolkswagen Lupo exhaust and emissions problems	2.05	1.08	1.8	24,196	18 to 24
Toyota MR2Toyota MR2 exhaust and emissions problems	2.33	1.25	1.8	30,113	17 to 25

Read this with care. A fail rate is not a measure of build quality. How far cars are driven, how they are used and how well owners maintain them all change it, and wear items such as tyres and brake pads are common fails. Compare a model only with cars of the same age. Methodology and limits.

Repair and cost

The usual repair is emissions fail repair.

No public source records the price of this whole job, and the time it takes varies from car to car, so we do not publish a single figure. Garages charge by the hour, so ask for a quote that lists labour time and parts. The rates below are what UK garages charge per hour.

The warning light or emissions reading is only the symptom. What the repair costs depends on what the diagnosis finds, so treat any figure as the starting point, not the full fix.

Local garage labour, per hour (65 shops)£78

Local garage, middle half£70 to £96

Main dealer labour, per hour (62 shops)£156

Main dealer, middle half£144 to £174

Median hourly rate charged for car repairs, from 1,058 local garage and 953 main dealer price quotes collected by the ONS, September 2025 to August 2026. The same shops are priced each month, so the number of shops is the real sample.

Emissions fail repair: cost and the models that need it more often

Related MOT defects

Oil leak, but not excessive4.59 per 100
Malfunction indicator lamp inoperative or indicates a malfunction1.46 per 100
Transmission oil leak, but not excessive0.59 per 100
Petrol exhaust Lambda reading after 2nd fast idle outside specified limits0.52 per 100
Emissions not tested unable to be completed0.29 per 100
Diesel exhaust emissions exceed manufacturer's specified limit0.26 per 100
Oil leaking excessively from engine0.12 per 100
Petrol exhaust emissions likely to be affected by an exhaust leak0.12 per 100
Petrol exhaust carbon monoxide content after 2nd fast idle exceeds default limits0.12 per 100
Emissions not tested0.11 per 100

All nuisance: noise, emissions and leaks defects All MOT defects Car repair costs

Buying a used car?

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Source

Contains public sector information licensed under the Open Government Licence v3.0. Source: DVSA anonymised MOT test data, class 4 normal MOT tests, 2022 to 2025, and the MOT inspection manual published on GOV.UK. Prices: ONS consumer price inflation price quotes, September 2025 to August 2026, UK.

MOT data updated 28 September 2026. Prices updated 22 September 2026.

Not affiliated with or endorsed by DVSA or the Office for National Statistics. How we calculate these figures · Data sources