The picture
C6: middle-of-the-pack on first-time pass
Across 473 MOT tests, the C6 returns 74.0% first-time pass — below the UK fleet average. The single most-logged Major fail is a defective headlamp lens. Worn suspension bushes and windscreen damage round out the top three. Average tested mileage sits at 104,699, which is the lens to read those failure rankings through. If you own one and the next test is close, the ranked list below is a sensible pre-test checklist.
Top ten reasons for rejection.
- 01
Headlamp reflector or lens slightly defective
18 occurrences · 3.8% of tests
- 02
A suspension pin, bush or joint excessively worn
18 occurrences · 3.8% of tests
- 03
Windscreen or window damaged or seriously discoloured but not adversely affecting driver's view
15 occurrences · 3.2% of tests
- 04
A transmission shaft constant velocity joint boot missing or no longer prevents the ingress of dirt etc
15 occurrences · 3.2% of tests
- 05
Warning device shows system malfunction
14 occurrences · 3.0% of tests
- 06
A rear registration plate lamp or light source missing or inoperative in the case of multiple lamps or light sources
14 occurrences · 3.0% of tests
- 07
Parking brake efficiency below minimum requirement
12 occurrences · 2.5% of tests
- 08
Significant brake effort recorded with no brake applied indicating a binding brake
11 occurrences · 2.3% of tests
- 09
ESC MIL indicates a system malfunction
9 occurrences · 1.9% of tests
- 10
A headlamp or light source missing, inoperative or more than ½ not functioning in the case of LED
8 occurrences · 1.7% of tests
Counts cover Major and Dangerous defects logged at test. Advisory items excluded so this shows why a car was rejected, not just what the tester flagged in passing.
Worst-case fix budget · top 2 failures
£90–£320
If every one of this C6's most-logged Major fails hit at the same MOT, that's the real-world UK garage range. Reality is usually one or two items, not all of them. Open the estimator →
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Tools that pre-empt a retest.
Picked against this car's top failure patterns. Affiliate links to Amazon UK — we earn a small cut at no cost to you. Disclosed up-front, doesn't shape the data.
Buying or keeping a C6?
Use the failure ranking as a pre-test checklist or a haggling lever. Treat the headline pass rate as a fleet-wide trend, not a guarantee on any individual car.
If you own a C6 and your last MOT looked nothing like the ranked failures above, that's normal — individual cars vary widely. The ranking shows the patterns testers flag most often across the country.