Fault code P2459 is called “Diesel Particulate Filter Regeneration Frequency” but in different programs it may be called differently. This fault designation applies to all vehicles equipped with OBD-II.
Technical description and explained code P2459
Stored code P2459 means that the transmission control module (PCM) has detected a fault in the diesel particulate filter regeneration (DPF) system. This error indicates that the regeneration process has not been completed properly.
DPF systems are designed to remove ninety percent of the carbon particles (soot) from the exhaust gases of diesel engines. Therefore, modern diesel cars smoke much less than cars of the past.
The DPF cleaning system is installed in the exhaust silencer, where the filter element is located. Large soot particles are trapped by the filter element, and the exhaust gases pass through it and out of the exhaust pipe.
When the filter element accumulates a certain amount of soot particles, it becomes partially clogged and the back pressure of the exhaust increases. The back pressure of the DPF is monitored by the PCM using a pressure sensor.
When the back pressure reaches a certain level, the PCM takes action to regenerate the filter element.
For the filter element to regenerate, the temperature inside the DPF must reach about 1200 degrees Fahrenheit. In most cases, a specialized injection system is used to do this.
Active DPF regeneration systems are automatically activated by the PCM, and the process occurs while the vehicle is in motion. Passive DPF regeneration systems require operator intervention (after the PCM issues a warning) and usually occur after the vehicle is parked.
If the PCM detects that the regeneration process has not been completed as specified, or if the exhaust pressure does not reach the desired level, fault P2459 may be stored and the malfunction control lamp will illuminate.
Symptoms of vehicle malfunctions
The main signal that an error P2459 has occurred is the Malfunction Indicator Lamp (MIL) is also known as the CheckEngine Light.
It can also be warning signs such as:
- Black smoke coming out of exhaust pipe.
- Floating revolutions, as well as attempts to stall at idle.
- Excessive engine temperature.
- Overheated body of exhaust system components.
- Other related trouble codes may also be present.
Fault P2459 is not considered very serious, but if the problem is not solved for a long time, the engine control module (ECM) can put the vehicle into emergency mode. This will cause the vehicle speed to be limited and engine power to drop.
Factors that can cause this error code
The error code P2459 can mean that one or more of the following problems have occurred:
- Defective DPF pressure sensor.
- Defective exhaust pressure sensor.
- Open or short circuit in DPF pressure sensor circuit.
- DPF pressure sensor tubing or hoses are clogged.
- Wrong or insufficient amount of regeneration fluid.
- Sometimes the cause is a faulty PCM module.
How to fix or reset OBD-2 code P2459
Some suggested steps for troubleshooting and fix the error code P2459:
- Read all stored data and error codes with an OBD-II scan tool.
- Clear the error codes from the computer memory.
- Test-drive the vehicle to see if error P2459 appears again.
- Visually inspect the wires in the DPF pressure sensor circuit.
- Check the tubes or hoses to the pressure sensor.
- Check the exhaust pressure sensor itself.
- Pay attention to the adequacy or amount of regeneration fluid.
- Test engine control module (PCM).
Diagnose and repair of problems
Diagnosing the P2459 problem should begin by checking the maintenance bulletins (TSB) for your specific vehicle. Your problem may be known, which can save you time and money during diagnosis.
Make a visual inspection of all the relevant wires and connectors associated with the system. Carefully inspect the harnesses that are near the hot exhaust pipes and manifolds.
Then connect the scan tool to the diagnostic port and retrieve any stored trouble codes. Record this information for further diagnosis, clear the codes and perform a test drive.
If the code does not clear immediately after the test drive, check the level and quality of the diesel exhaust fluid, and then activate the DPF regeneration system.
The regeneration procedure may have been inadvertently interrupted by another, unrelated problem which has been corrected. The regeneration process can now be successfully completed after clearing the codes.
In case fault P2459 remains, it is necessary to test the DPF pressure sensor with a multimeter. If the sensor when tested does not meet the manufacturer’s resistance specifications, it must be replaced.
On which vehicles does this problem occur most frequently
Fault code P2459 can occur on different vehicles but there are statistics on which brands this occurs most often. Here is a list of some of them:
- Chevrolet
- Dodge (RAM)
- Ford (Focus)
- GMC
- Land Rover
- Mazda (5, 6, CX-7)
- Mercedes-Benz
- Opel (Insignia)
- Volkswagen (Passat)
Fault code P2459 can sometimes be found with other errors. The most common are the following: P0304, P2458, P2463, P246B, P260E.
