Exhausts, CATS and accessories 32 www.aftermarketonline.net APRIL 2025 Troubleshooting EGR systems Nissens Automotive highlights exhaust gas recirculation system issues and solutions As vehicle manufacturers (VMs) strive to limit the impact that combustion engines have on the environment, the majority of new vehicles are equipped with an exhaust gas recirculation (EGR) system. However, depending on how the vehicles are driven and the quality of fuel used can lead to high rates of failure and replacements business for the aftermarket. A fault with the EGR valve, for example, can lead to severe onboard diagnostic errors that can result in the engine being set to limp mode and may provoke failures in other parts of the system. Common reasons for EGR system failure include unclean combustion, frequent short distance travel patterns, excessive thermal stress and moisture/contamination of the fuel. With this in mind, Nissens Automotive is able to provide workshops with a premium quality aftermarket solution and the technical support they require. Although there are several elements within the EGR system, the valve is central, and the part that is most often replaced. However, before doing so, it is important to undertake the correct diagnosis to find any underlying faults that may have caused or contributed to the problem the vehicle was brought in for, which will require some troubleshooting. However, before concluding that the EGR valve has failed, it is highly recommended to thoroughly inspect the complete system, including engine intake, exhaust, and emissions control components. It is also important to understand that the engine control unit monitors several sensors and components to maintain optimal performance and comply with emission standards, so if a problem occurs in one of the related systems, it can affect the EGR system’s function and result in error codes. Therefore, a thorough diagnosis is needed, including inspecting and testing components to identify the exact cause of any error codes. If it turns out that the valve does need to be replaced, it must be calibrated with the ECU to function correctly. This includes calibrating the EGR system to work seamlessly with a new or replaced EGR valve, or its related components. The EGR adaptation process is critical for maintaining proper engine performance and reducing emissions and should be carried out by experienced technicians using appropriate diagnostic equipment. After replacing the EGR components, the EGR adaptation process begins with the initialisation of the ECU. During the adaptation process, the ECU enters a ‘learning phase’ — collecting data from the new EGR component to understand its specific characteristics and behaviour, such as voltage readings, response times and temperature ranges. The ECU then calibrates itself to work optimally with the new EGR component. Once calibration is complete, it is essential to verify the correct operation of the EGR system. If error codes related to the EGR system were stored in the ECU before the adaptation process, these codes must be cleared to ensure that the vehicle’s ECU is not operating in a limp or reduced performance mode. Visit https://nissens.com/egrsystem-parts to find out more. Common issues with the EGR system can be experienced by: O Engine irregular idling or jerking O Engine ‘chattering noise’ O Insufficient engine performance (lower RPMs in petrol engines and higher RPMs in diesel engines) O Engine limp-mode activation O Engine misfires O Illumination of the check engine light, often accompanied by diagnostic trouble codes.
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