Technical Description of OBD-II Trouble Code
The efficiency of the Diesel Particulate Filter is below the required threshold for Bank 1.
What does that mean?
This diagnostic trouble code (DTC) is a generic powertrain code that applies to all makes and models of vehicles (1996-newer). However, the specific repair steps may vary slightly depending on the model.
The trouble code “P2002 diesel particulate filter efficiency below threshold” is related to an emissions control device. It is installed on 2007 and later diesel vehicles to reduce the soot emitted from their exhaust. This DTC is commonly seen in Dodge, Ford, Chevrolet, or GMC diesel pickups, but it can also occur in other diesel cars such as VW, Vauxhall, Audi, Lexus, etc.
The DPF (diesel particulate filter) is shaped like a catalytic converter and is located in the exhaust system. It contains a matrix of compounds, including cordierite, silicon carbide, and metal fibers, which effectively eliminate soot by 98%.
Here is a cutaway photo of a diesel particulate filter (DPF):
The DPF creates a slight back pressure during operation. The vehicle’s ECU (computer) has pressure-feedback sensors on the DPF to monitor its functionality. If the ECU detects a discrepancy in the pressure limits for two running cycles, it will set the code P2002 to indicate a malfunction.
However, there is no need to be overly concerned as these devices have a regenerative capability to burn off the accumulated soot and return to full service. They have a long lifespan.
Once the regeneration process occurs, the check engine light will go out and the code will clear itself. This is known as a soft code, as it indicates a fault in real time and erases as the fault corrects itself. A hard code, on the other hand, remains until the repair is completed and the code is manually erased with a scanner.
All vehicles require a device to eliminate the expulsion of oxides of nitrogen into the atmosphere, which would not be present otherwise. This is not only harmful to your health but also to the atmosphere. Gasoline engines use a catalytic converter to solve emissions, while diesel engines face more challenges.
Due to the high cylinder head temperatures in diesel engines, which result from relying on the heat of super compressed fuel for spontaneous combustion, there is a serious risk of producing oxides of nitrogen. NOx is produced under extremely high temperatures. To address this issue, engineers introduced EGR (exhaust gas recirculation) to dilute the incoming fuel charge and reduce the head temperatures, thus reducing the formation of Nox. However, the exhaust temperatures in a diesel engine are too high, which would only worsen the problem.
To solve this problem, engine coolant is used to cool the engine oil and EGR pipe, reducing the cylinder head temperatures below the threshold necessary for the formation of Nox. This solution has been quite effective. The DPF serves as the final line of defense against emissions by eliminating soot.
NOTE: This P2002 DTC is the same as P2003, but P2002 refers to bank 1, which is the side of the engine that contains cylinder #1.
Symptoms
Symptoms of a P2002 DTC may include:
Potential Causes
The potential causes for this DTC may include:
Diagnostic Steps & Possible Solutions
The solutions for this issue are somewhat limited since the DPF is not defective but temporarily clogged with particulates from soot. If the check engine light is on and the code P2002 is set, start with a visual inspection to eliminate potential issues.
Inspect the DPF on Bank #1 for loose connections on the engine side where it mounts to the exhaust.
Inspect the differential pressure sensors located on the front and rear of the DPF (bank 1). Look for burnt wires or loose or corroded connectors. Separate the connectors and check for bent or corroded pins. Ensure that the sensor wires are not resting on the DPF. Start the truck and check for leaks on or around the unit.
If everything appears to be in good condition after the above steps, drive the truck for approximately 30 minutes at highway speeds to raise the exhaust temperature enough to regenerate the DPF. Alternatively, idling the engine at 1400 rpm for approximately 20 minutes can achieve the same results.
If the problem persists after driving at highway speeds, it is best to take the vehicle to a shop and have them connect it to a diagnostic computer, such as the Tech II. This is a relatively inexpensive procedure, and they can monitor the sensors and the ECU in real-time operation. They will be able to observe the signals from the sensors and determine if the ECU is attempting the regeneration process. This will quickly identify any faulty components.
If you primarily drive in-town and experience recurring issues, there is another solution. Most shops can reprogram your computer to prevent the regeneration process in a few minutes. Additionally, you can remove the DPF and replace it with a straight pipe (if permitted in your jurisdiction). However, do not discard the DPF, as it can be valuable if you decide to sell it or need it in the future.
NOTE: Some modifications, such as “cold air intake” (CAI) kits or cat-back exhaust kits, may trigger this code and could also affect your manufacturer’s warranty. If you have made such modifications and encounter this code, reinstall the stock part and check if it resolves the issue. Alternatively, contact the kit manufacturer for advice on addressing this known issue.
