Error Code P2002 is defined as Diesel Particulate Filter Efficiency Below Threshold Bank 1, which refers to an issue in the efficiency of the particulate filter in the exhaust, which is most likely caused by faulty filter or sensor, or exhaust leak.

This error code is diesel-specific OBD-II code, which means it applies to most vehicles equipped diesel engines. Specifications on the definition, troubleshooting, and repairs, of course, vary from one make and model to another.

Definition

Diesel engines usually offer better torque and fuel economy than gasoline engines. However, the diesel fuel itself produces more “soot” (PM2.5 and PM10, particulate matter that is less than 2.5 µm and 10 µm in size), which is considered hazardous to both the atmosphere and human health. Modern diesel engine technology and fuel, on the other hand, has been refined to eliminate many of these emissions. There are, of course, still some circumstances when more soot is generated. This usually happens when the engine is not running hot, such as in stop-and-go traffic and short trips.

To capture these PM emissions, a Diesel Particulate Filter (DPF) is included in diesel engine vehicles. They’re collected during low-load conditions. Stored PMs are kept until they can be burned off, which is in high-load conditions, such as long trips or uphill driving. The PCM (powertrain control module, also known as ECM or engine control module in other vehicle makes) will command more fuel injection, increasing the DPF temperature of 450˚C to 600˚C (840 °F to 1,112 °F). That is enough to complexly oxidize the stored PM emissions, which clears the filter without releasing the harmful emissions to the atmosphere. They call this process DPF regen (regeneration), which typically automatically takes place every 250 to 500 miles.

The DPS (Differential Pressure Sensor) is used by the PCM to measure the efficacy and capacity of the DPF. The DPS measures the difference in pressure before and after the DPF. A clean filter will not provide much resistance to the exhaust close, leaving little to no measurement to the DPS differential. As the DPF collects more emissions, the resistance increases, affecting the gradual increase in pressure differential. Depending on the vehicle threshold, certain vehicles may trigger the DPF regen cycle, but only with the right conditions. Some vehicles may trigger the regen cycle at about 15% capacity.

If the conditions are insufficient for the regen cycle to take place, the DPF will continue collecting PM emissions until they are. Again, the DPF still have a certain capacity, which the PCM continues to monitor through the DPS. Again, depending on the vehicle, once the DPF reaches its full capacity, (about 20% to 80%), the PCM will alert the driver regarding the need for a DPF regen cycle. If this happens, the Check Engine light will come on, and the Error Code P2002 will be set.

Common Symptoms

Symptoms for this code depend on the failure mode. As with other error codes, it activates the Check Engine light and registers the code to vehicle’s system. In many cases, there may not be any observable symptoms other than the Check Engine lights, but for some vehicles, the PCM may put the vehicle on ‘Limp Mode,’ which restricts both the performance of the engine and the transmission. Other vehicles with overcharged DPG may show other symptoms like:

  • Hard starting
  • Poor acceleration
  • Poor fuel economy

Concurrent trouble codes may also appear, such as problems referring to the EGR (exhaust gas recirculation) fuel trim faults, and turbocharger faults, even if there are no faults in these systems.

Possible Causes

Many possible causes lead to this error code, which mostly depends on the year and make of the vehicle. Here are common possible causes:

Driving habits – stop-and-go traffic and short trips overload the DPF, while the vehicle never gets hot enough to conduct a DPF regen cycle.

Overcharged DPF – usually happens in poorly-maintained engines or diesel fuel with high sulfur content. Some biodiesel fuels contain more than the normal level of soot, which can be excessive for the vehicle, and DPF regen cycle may not solve the problem, as it requires replacement.

Defective DPS – some factory-installed DPS are actually of poor quality, causing manufacturers to release updated and better quality parts.

Reflash – this is a software problem. Check with your dealership service center if they have addressed the software update for this error code for your vehicle.

Other possible causes include:

  • Defective particulate filter
  • Defective exhaust back pressure sensor
  • Exhaust leak
  • Poor quality of diesel fuel

How to Check

To diagnose this code, conduct a visual inspection of both the particulate filter and the back pressure sensor and associated wirings.

After checking those components, take the vehicle for a test drive with an OBD-II scanner connected to track the back pressure sensor readings. It would be best to have your mechanic with you for these diagnosis steps.

If Bank 1 seems to be sending mixed signals than the Bank 2, then your mechanic will conduct further troubleshooting of the sensor to determine whether the particulate sensor must be replaced.

How to Fix

The most common solution for this code is to manually put the vehicle on the DPF regen mode by using a scan tool or taking the vehicle out on the highway for a little longer to let the heat burn off the stored PM emissions.

Clearing the diesel particulate filter

Changing diesel fuel

Replacement of the particulate filter

Replacement of DPS with a manufacturer-specific part. You can check this with your dealership service center to see if your vehicle comes with the most recent version.

Diesel particulate filters were first used in the mid-2000s. If your vehicle is older, then there’s a good chance it doesn’t come with this component, and you will not encounter this error code.