Will roadworthiness tests penalise drivers in France for removing emission-limiting liquid?

Various social media posts are making the rounds in France claiming diesel drivers who deactivate emission-limiting technology on their vehicles will fail roadworthiness tests. 

The posts mention the AdBlue system, which is installed in some diesel vehicles to help reduce emissions, but some drivers say it increases the chance of vehicle breakdown.

What is AdBlue?

Modern diesel vehicles with Selective Catalytic Reduction come equipped with AdBlue as standard. 

This is a blue liquid that is injected into the exhaust system, reducing the levels of nitrogen oxide (NOx) emitted from the exhaust system by up to 90%. 

Despite the aims of reducing emissions, some drivers criticise the liquid – which is required to be installed in certain diesel vehicles – for increasing the risk of breakdown.

The liquid can sometimes degrade above 25C, and in other cases crystalise. 

At best, this can clog pipes and lead to deformation of the AdBlue tank (located near the exhaust), but at worst can lead to total engine failure, requiring extensive and costly repairs.

Are contrôle technique tests affected?

This has led to numerous motorists deactivating the system, which can be done by a professional in a garage for around €250.

Despite the claims on social media however, doing so does not cause drivers to fail their roadworthiness tests (contrôle technique, or CT).

In addition, “there are no plans to change the regulations… either for checking pollutant emissions or for checking vehicle safety features,” said motorist union Mobilians. 

It also noted that other social media posts around changes to CT tests next year – including removing paint, and stricter checks on seatbelts – are also false. 

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