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Emission Technology Troubleshooting Diesel Oxidation Catalyst - DOC Typically, it is not the DOC that fails, but something that has gone wrong upstream. Excessive black smoke and low duty cycles will cause DOC face plugging. In such a case the DOC will have reduced performance and cold regeneration may occur. Eventually, the face will be plugged, creating restricted exhaust flow and excessive back pressure. Common DOC Failures The HC injector is clogged: Fuel can mix with soot to clog the injector. EGR coolant leaks & turbo fails: Oil and coolant sent downstream will contaminate the precious metal coating, leading to DOC inactivity. An inactive DOC will struggle to raise the temperature needed for a proper regeneration. The air filter is full: The DOC needs air when it ramps up to go through regeneration. If the air filter is full or clogged, the DOC will not receive enough air. When do you see failures in the DPF? Diesel Particulate Filters can fail due to upstream events or due to high mileage. Common DPF Failures Engine and Fuel system failures: Over-fueling injectors or a leaking aftertreatment injector will cause temperatures to raise too high resulting in the substrate melting or cracking. Oil entering the exhaust will also cause an uncontrolled thermal event. EGR cooler leaks & turbo fails: Oil and coolant sent downstream will contaminate the PGM coating. Air induction system failure: A restricted air intake system will cause excessive black smoke and result in frequent regens. Milege and replacement intervals: A DPF, like any other filter, has a limited-service span. It is advised to adhere to the cleaning interval specified by your engine manufacturer. For optimal performance, we recommend replacing the DPF with a reconditioned or new unit after reaching 125,000 miles for distribution vehicles and after every 250,000 miles for long distance vehicles. An alternative option is to clean the filter, which however is likely to reduce this service span. Visible soot from tail pipe: The DPF may eventually crack due to excessive and unusual thermal conditions, allowing unfiltered exhaust to escape. Physical damage, excessive amount of trapped soot, or repetitive improper cleaning may lead to these cracks, and the filter should be replaced by a new unit as soon as possible. Selective Catalytic Reduction - SCR Typical SCR failures have their root causes in other system components that stop working properly, such as the Mechatronics controlling the system, or engine-related failures. Common Failures causing problems with SCR Failures in DEF system: Leaking DEF injectors will cause DEF crystallization in the SCR. In addition, using DEF that is not the proper concentration or is contaminated will cause issues with the SCR. Failures upstream: Contaminants such as engine oil, coolant, or other impurities can damage the SCR catalyst, reducing its efficiency in converting NO into harmless gases. X Mechanical defects of substrate: Over temperature from an upstream issue will cause the substrate to crack or lose its ability to convert NO . X 8
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Frequently asked questions about NO X sensors The NO X (Nitrogen Oxides) sensor is crucial for the proper functioning of an SCR system, but it is also a delicate piece of technology that operates in a harsh environment. As a result, failures may occur more frequently than for other parts in the exhaust system. This sensor is typically a high-temperature device that measures the level of NO X in exhaust systems before and after the SCR catalyst. The information gathered is used by Engine Controls to calculate the exact amount of Diesel Emission Fluid to be dosed at that moment, achieving the necessary reduction of Nitrogen Oxides (NO X ), as strictly regulated by authorities worldwide. All Dinex NO X sensors meet OE criteria and undergo calibration and testing at specialized facilities. These sensors are available for Cummins, Detroit, Freightliner, International, Kenworth, Paccar, Peterbilt, and Volvo, as well as a wide range of off-road applications. What is the average life of a NO X sensor? About 6,000 hours or 200,000 miles (300,000 km). Does the sensor have the same calibration as OE (ppm levels)? Yes, while AEM sensors generally have a slightly wider tolerance zone compared to OE sensors, Dinex sensors maintain the same high level of accuracy as OE. Can I drive with a bad NO X sensor? Yes, but the engine might operate in safe mode (reduced power and speed), and the emissions might exceed the specified regulations. How can I determine if the sensor comes installed with the correct software? The only way is to compare Continental cross-references. What is the difference between Dinex NO X sensors and sensors made by other producers? Dinex adds value to the sensor by establishing continuous improvements to the product range to solve problems and guide our customers to make the correct choice. What should I do when the sensor does not work immediately after installation? Double check if the correct cross-reference has been used and make sure all the electrical connections are good. It is also important to run a complete system diagnostic to see if there are other issues that could be causing the NO X sensor failure, such as short or open circuit. Other SCR system components can also affect the NO X sensor, such as the DEF pump. For more information, installation guides, videos, and resources on NO X sensors, visit our website, where Dr. NO X is ready to assist you. STRON G GY STER SM ER FA ART TECHNOLO Think you know Aftermarket NO X sensors? Then you haven’t tried Dinex Generation 2.0 sensors: Every bit as good as OE – only more affordable 9
