Exhaust gas pressure sensor – Step-by-step diagnosis

What is the role of the exhaust gas pressure sensor?

For many years, manufacturers of today’s cars and trucks have been subject to top-down obligations to actively combat negative climate change. This is a conscious policy that aims to combat increasing environmental pollution and improve air quality.

The best example of such restrictions are the EU exhaust emission standards (currently Euro 6), which regulate the maximum legally permissible concentration of harmful chemical compounds and solids contained in vehicle exhaust.

Meeting the standards set by the EU is done in several ways, but one of the most effective is the active systems of filtration of gases emitted by the exhaust system of a vehicle. At their heart is a special exhaust gas pressure sensor, which continuously monitors the pressure difference. The data obtained from it help the engine control unit to calculate the effectiveness of the filtration.

The exhaust gas pressure sensor also estimates how full the particulate filter is, so that it can signal the car’s on-board computer to activate the DPF active afterburning mode (in the case of petrol vehicles, GPF or FAP) as required. This process is carried out by feeding a richer fuel mixture into the engine compartment, which automatically raises the combustion temperature, thus helping the particulate filter to regenerate itself.

It is worth mentioning at this point that the exhaust gas pressure sensor can also signal that the filter is overfilled, and thus the need to go to an authorised service centre and carry out the necessary repair work.

What problems does a faulty exhaust gas pressure sensor cause?

Unfortunately, just like any other device, the exhaust gas pressure sensor can break down at some point. However, this is a relatively rare occurrence, as these sensors are built for long-term, trouble-free operation.

If a fault is detected, it is essential that it is repaired as soon as possible – the exhaust gas pressure sensor is a key component of the particulate filter system. Its correct functioning allows the vehicle’s on-board computer to detect an excessive amount of soot, thus giving the possibility to activate the active burn-out programme.

However, if the exhaust gas pressure sensor breaks down, its erroneous readings will confuse the control unit, resulting in irreversible clogging of the particulate filter and, in extreme cases, even damage to the vehicle’s engine.

Malfunctioning exhaust gas pressure sensor – symptoms of failure

The first and most obvious sign that the exhaust gas pressure sensor needs to be replaced is the light on the dashboard. Depending on the make of car, the failure may also be indicated by a specific error code, and in newer premium cars by an appropriate text message on the on-board computer display.

However, it is worth actively “listening” to the operation of your car, because early self-diagnosis can help avoid many of the problems that the exhaust gas pressure sensor can cause. Symptoms that can also accompany this fault are:

• noticeably increased fuel consumption caused by continuous injection of too rich a mixture;
• delayed response to the accelerator pedal and much poorer engine performance due to obstructed flow of exhaust fumes through the exhaust system;
• increased engine operating temperature;

Of course, the above symptoms may be caused by something completely different, so it is important to observe the car’s performance over a longer period of time. However, if the symptoms persist, it is recommended to take the car to a qualified mechanic, who will professionally diagnose the exhaust gas pressure sensor.