This is the reason many cars fail the ITV inspection, and it can turn out to be very expensive

The ITV is one of those obligations we have to go through with the car every year, and once the car is getting on in years it becomes an endless source of stress and nerves. Passing or failing the ITV can mean an extra year of life for the car, a considerable expense to pass the Vehicle Technical Inspection again with everything in order, or having to take the car off the road and think about buying a new one.

The causes are very varied, although there is one that is very common and that is responsible for 16.2% of ITV failures. It is not the main cause, but it is one of the most common, in third place, and one that is growing because of the ageing of the car fleet. In fact, in 2018 1,355,508 vehicles failed to pass the ITV for this reason and had to return to the inspection station after visiting the workshop.

Exhaust gas emissions, a cause of ITV failure

ITV technicians carry out two types of control of polluting emissions on vehicles, with which they detect possible faults in this area and issue an unfavourable or favourable report accordingly. Euro 5 and Euro 6 cars undergo an electronic check, in which they read data from the on-board computer and verify that everything is in order.

For Euro 4 cars the control of polluting gases is carried out by inserting a probe into the exhaust pipe. Failing this check and recording more polluting emissions than permitted is considered a serious defect, and the car will not be able to pass the ITV inspection.

Causes of exhaust gas emissions

High exhaust gas emissions can be caused by several reasons. The age of the car is fundamental, and the various faults that can occur due to age are caused by a lack of maintenance, a fault in the GR valve or the injectors.

Diesel cars are the ones that most often fail in this respect. This fault is often caused by a lack of maintenance. In this case it can be solved simply by checking the circuit and replacing the filters or whatever else is necessary. In this case everything can be fixed for a minimal cost, between 60 and 70 euros.

Another fault can come from a fault in the GR valve, which is the one that allows the gases coming from the engine to recirculate. It is responsible for sending the “bad” gases to the exhaust and the good ones return to the engine. If it does not work properly, it will need to be replaced, and that carries a somewhat higher cost, which can reach 300 euros.

Finally, the injectors are another point that can be the reason the car fails the ITV because of exhaust gas emissions. Injectors age over time. As they get older, the injectors can start to malfunction and cause more petrol or diesel to be injected.

This is one of the most expensive faults that can occur, since replacing just two injectors would raise the workshop bill to 500 euros. These faults, which carry a considerable cost, lead many drivers to prefer to give up on the old car and buy a new one or at least a used one, newer and better maintained.

The key to avoiding these problems and keeping the car for a long time is maintenance. The ageing of the car fleet means many problems appear in cars, so time and money must be devoted to keeping the car in good condition. Although it is an annual cost, it is far cheaper than finding a fault of this magnitude when taking the car for its ITV.