The need to reduce nitrous oxide emissions from diesel has been a major imperative in recent years, in order to minimise toxic air pollution. However, a major means of doing it has brought drivers quite a few headaches when the system has not worked properly.
AdBlue has been an essential component in selective catalytic reduction (SCR) systems, with this diesel exhaust fluid helping capture many emissions and turn them into less harmful gases. It does this by being injected into the gas and producing a chemical reaction that turns some of these harmful substances into benign ones.
This helps reduce the amount of pollutants being released into the air from your exhaust, which otherwise produce particulate matter and contribute to smog, ozone and acid rain, all of which are bad both for human health and the wider environment.
Under UK law, most diesel vehicles only meet the Euro 6 test standard on nitrous oxide pollution when they have SCR systems working with AdBlue as an essential component.
Indeed, as stated by organisations like the AA, AdBlue is something your car can’t do without, stating that “if you run out of it, your car won’t start.”
That may sound quite extreme, but there is a reason for it. Quite simply, while there are ways of carrying out AdBlue removal, disabling the system so that a car can run without it, the result will be that it is likely to be running illegally and would fail its MOT, unless it is being used off-road.
To ensure that the SCR is running legally, an absence of AdBlue will be picked up by sensors (the same kind of device that would tell you if your petrol tank was empty) and this will lead to declining performance driving, plus the car not starting again next time.
AdBlue removal can be carried out to disable this system. You may read articles about this explaining how it improved performance and reduced running costs, including on maintenance of the SCR system and the money you would otherwise spend on AdBlue.
However, whether this is through disabling the detection system or fitting AdBlue emulators that fool your vehicle’s systems into thinking the AdBlue system remains in place, the bottom line is that it still makes your vehicle illegal to drive on UK roads.
The legitimate reason to remove AdBlue is when the SCR system is faulty and the AdBlue function is a part of it. However, this must be fixed and then fitted back in place; you can’t just do without it.
A good example of this, for example, may be if the warning light is on despite AdBlue being present, risking that the engine will not start even though the AdBlue tank is not empty.
Another case would be if the system is faulty so that the AdBlue fluid is not being injected into the exhaust mix, preventing the SCR from doing its job and making the vehicle emissions levels illegal.
Common AdBlue system issues also include pump failure, failures in the SCR catalyst and nitrous oxide sensor failures.
Getting these fixed ensures your SCR system functions as it should, keeping down pollution levels while ensuring your vehicle is legally compliant, the engine switches on, and that you can get back on the road.