Technical Description of OBD-II Trouble Code
Bank 2 Diesel Particulate Filter Efficiency Below Threshold
What does that signify?
This generic powertrain code (DTC) is applicable to all vehicle makes and models (1996-newer). However, the specific repair steps may vary slightly depending on the model.
The DTC is related to a diesel particulate filter, an emissions control device. It is installed in 2007 and later diesel vehicles to eliminate soot from the exhaust. While this DTC is commonly seen in Dodge, Ford, Chevrolet, or GMC diesel pickups, it can also be triggered in other diesel cars like VW, Vauxhall, Audi, Lexus, etc.
The diesel particulate filter (DPF) is shaped like a catalytic converter and is positioned in the exhaust system. It contains compounds such as cordierite, silicon carbide, and metal fibers that effectively eliminate soot.
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 sensors detect a discrepancy in the pressure limits for two running cycles, the code P2003 is set to indicate a malfunction.
However, there is no need to be overly concerned as these devices have a regenerative capability to burn off 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. Oxides of nitrogen are harmful to both human health and the atmosphere. Gasoline engines use a catalytic converter to solve emissions, while diesels face more challenges.
Due to their reliance on the heat of super compressed fuel for spontaneous combustion, diesel engines have very high cylinder head temperatures, creating an ideal environment for the formation of oxides of nitrogen. NOx is produced under extremely high temperatures. To address this issue, engineers introduced exhaust gas recirculation (EGR) to dilute the incoming fuel charge and reduce head temperatures, thus reducing NOx. However, the high exhaust temperatures in diesel engines would compound the problem.
To overcome this, engine coolant is used to cool the engine oil and EGR pipe, reducing cylinder head temperatures below the threshold necessary for the formation of NOx. This solution has been effective. The DPF serves as the final line of defense against emissions by eliminating soot.
NOTE: The P2003 DTC is the same as P2002, but P2003 refers to bank 2, which is the side of the engine that does not contain cylinder #1.
Symptoms
The symptoms of a P2003 DTC may include:
Potential Causes
The potential causes for this DTC may include:
Diagnostic Steps & Possible Solutions
The solutions for this DTC 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 P2003 is set, start with a visual inspection to eliminate potential issues.
Inspect the DPF on Bank #2 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 2). 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 for DPF regeneration. Alternatively, idling the engine at 1400 rpm for about 20 minutes can achieve the same results.
If the problem persists even after driving at highway speeds, it is best to take the vehicle to a shop and have them connect it to a diagnostic computer like the Tech II. This is a relatively inexpensive process, and they can monitor the sensors and 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 holds significant value and can be sold or used in the future if needed.
NOTE: Certain 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.
