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Technical Description of OBD-II Trouble Code
Frequency of Diesel Particulate Filter Regeneration
What does that signify?
This diagnostic trouble code (DTC) is a generic powertrain code that applies to all vehicles manufactured from 1996 onwards (Ford, Dodge, GMC, Chevrolet, Mercedes, VW, etc.). While it is a generic code, the specific repair steps may vary depending on the make and model of the vehicle.
If a stored P2459 code is encountered, it indicates that the powertrain control module (PCM) has detected a malfunction in the diesel particulate filter (DPF) regeneration system. The P2459 code signifies that the regeneration process has not been completed with the desired frequency over a programmed period of time or distance. This code is specific to diesel-powered vehicles.
DPF systems are designed to eliminate ninety percent of carbon particles (soot) from the exhaust of diesel engines. They play a crucial role in helping automakers meet federal regulations for clean-burning diesel vehicles. If you appreciate the fact that modern diesel vehicles produce significantly less smoke than their predecessors, you can thank DPF systems.
Most DPF systems operate in a similar manner, although there are various designs. The DPF housing is typically a large steel muffler-shaped device that contains a filtration element. Ideally, the filtration element traps soot particles while allowing exhaust gases to flow through and exit the tailpipe. The DPF usually contains wall fibers that attract larger soot particles as they enter the housing, but some models use systems with a loose web assembly that fills almost the entire housing. The ports in the filtration device are precisely sized to trap larger soot particles while allowing exhaust gases to flow through.
When the filtration element becomes partially clogged with a certain amount of soot particles, it becomes saturated, leading to an increase in exhaust pressure. The PCM uses a pressure sensor to monitor the back pressure in the DPF. When the back pressure reaches a specific level, the PCM initiates the regeneration process for the filtration element. The temperature inside the DPF needs to reach approximately 1,200 degrees Fahrenheit for effective regeneration of the filtration element. In most cases, a specialized injection system is used to achieve this. An electronically controlled injection sprays a flammable chemical, such as diesel fuel or diesel exhaust fluid, into the DPF. The trapped soot particles are then incinerated and released into the atmosphere as ions of nitrogen and water through the tailpipe.
DPF systems that are activated automatically by the PCM are known as active DPF systems. This process usually occurs while the vehicle is being driven. Systems that require input from the operator are referred to as passive systems. These systems are activated after the PCM displays a cautionary warning, and most of the process takes place while the vehicle is parked. The passive regeneration system procedure may take several hours to complete. Consult your vehicle owner’s manual or service manual to determine which type of DPF system your vehicle is equipped with.
If the exhaust pressure fails to reach the desired level or if the PCM detects that the regeneration process has not occurred with the desired regularity, a P2459 code will be stored, and a malfunction indicator lamp may illuminate.
Symptoms & Severity
Addressing a P2459 code should be considered a priority because DPF regeneration is crucial for maintaining the desired exhaust back pressure. Symptoms of a P2459 code may include:
Causes
Possible causes for the occurrence of this code are:
Diagnostic and Repair Procedures
It is always advisable to check for technical service bulletins (TSB) specific to your vehicle as a starting point. Your issue may be a known problem with a known solution provided by the manufacturer, which can save you time and money during the diagnosis process.
To diagnose a P2459 code, you will need a vehicle service manual or its equivalent, a scanner, and a digital volt/ohmmeter.
I recommend inspecting all system-related wiring harnesses and connectors, paying special attention to harnesses located near hot exhaust pipes and manifolds. This can save time in the future. It is also a good idea to load test the battery, check battery terminal ends, battery cables, and alternator output at this time.
Next, connect the scanner to the diagnostic port and retrieve all stored trouble codes and freeze frame data. Write down this information before clearing the codes and test driving the vehicle, as it can be helpful later. Test the level and quality of the diesel exhaust fluid and activate the DPF regeneration system if the code fails to reset immediately after test driving. If the regeneration procedure was interrupted unintentionally due to another unrelated problem that has been resolved, the regeneration process may be completed correctly at this time.
Follow the manufacturer’s recommendations for testing the DPF pressure sensor using the digital volt/ohmmeter if the code fails to reset immediately. If the sensor does not comply with the manufacturer’s resistance specifications, it must be replaced.
Additional diagnostic notes:
Professional Service
While we always recommend seeking mechanical solutions for this issue, if that is not possible, we offer the option to permanently delete this specific DTC. All other codes will continue to function. If you are interested in this option, please upload your ECU file to our portal.
