|Code||Fault Location||Probable Cause|
|P200D|| Diesel particulate filter (DPF), bank 2 - over-temperature condition |
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Table of Contents
- What Does Code P200D Mean?
- Where is the P200D sensor located?
- What are the common causes of code P200D?
- Get Help with P200D
What Does Code P200D Mean?
OBD II fault code is a generic code that is defined as “Diesel Particulate Filter Over Temperature Bank 2”, or sometimes as “Diesel Particulate Filter (DPF) High Temperature”, and is set when the PCM (Power Control Module) detects that the diesel particulate filter is operating at an abnormally high temperature. Note that an over temperature condition is almost always caused by an excessive amount of soot in the diesel particulate filter. Also, note that “Bank 2” refers to the DPF (Diesel Particulate Filter) that is fitted to the exhaust system of the bank of cylinders that does not contain cylinder #1, and that DPF related codes affect only diesel applications.
NOTE: While the effective operating temperature of most diesel particulate filters is about 600oC (1 1200F) during the regeneration process, this temperature reduces to between 3500C – 4500C (6600F – 8400F) if a fuel-borne catalyst is used to initiate and sustain the regeneration process. In practice though, there is no single effective regeneration temperature that applies to all applications, since this temperature is wholly dependent on both the chemistry employed in the DPF, the type of DPF used, as well as the regeneration process that is used on any given application.
The purpose of a DPF is to reduce harmful diesel exhaust emissions by capturing the solid, particulate matter commonly known as “soot” in diesel exhaust, and to hold onto the soot until a predetermined amount of soot had been collected. When this point is reached, the PCM will initiate a process of regeneration, which usually involves raising the temperature of the DPF filter element to the point where the collected soot is burned off. During the regeneration process, which can be active, passive, or forced, the accumulated soot is converted into fairly innocuous substances, while at the same time, the DPF is cleaned out, i.e., regenerated, to allow it to begin capturing soot again.
In terms of operation, the PCM uses input data from exhaust pressure sensors, as well as exhaust temperature sensors to gauge the efficiency level of the DPF. IF the DPF system is fully functional, the PCM uses this input data to determine the DPF’s load, which the PCM interprets as the total amount of soot that had collected in the DPF.
When this load exceeds the soot load limit that applies to that application, the PCM initiates both the introduction of a reductant (typically urea) and additional fuel into the DPF to raise the DPF’s internal temperature to the point where regeneration can take place. On other applications, the PCM makes adjustments to the injection timing and other systems, which also has the effect of raising the exhaust temperature to the point where regeneration takes place. Note that in the latter case, no chemicals or additional fuel is introduced into the exhaust system.
Below are some details of the most commonly used regeneration processes-
Active regeneration uses the soot load limit and input data from exhaust backpressure sensors to either initiate adjustments to the injection timing to increase the exhaust temperature, or to activate electrical heaters in the DPF. Depending on make and model, the PCM will typically initiate a regeneration of the DPF every 400 km – 600 km ( 250 miles – 370 miles), but note that this also depends on whether the vehicle is used for city or highway driving, average engine loads, fuel quality, and the overall mechanical condition of the engine, among other factors. Typically, though, an active regeneration usually takes around 10 minutes or so to complete.
In passive regeneration, a reductant is added to the exhaust stream to raise the temperature to the desired level. However, some manufacturers use a stream of atmospheric air to achieve that same result, since the introduction of oxygen can oxidize carbon reasonably effectively without the need for additional fuel of chemicals. Passive regeneration can take up to 30 minutes to complete.
Some manufacturers use DPF catalysts that allow the use of a combined passive-active regeneration system. In these cases, the DPF regenerates passively at sustained high seeds since the exhaust temperature is high enough under these conditions to allow for effective regeneration, while an active regeneration may be initiated by an engine management strategy during periods of low speed city driving.
While there are many reasons why DPF regeneration processes either do not initiate, or complete, not all of these possible reasons involve failures or malfunctions of the system. For instance, long periods of city driving can prevent the process for starting or completing, and the only way to regenerate the DPF in these cases is to perform a forced regeneration by following exact, specified procedures that can typically only be performed with the aid of manufacturer specific diagnostic equipment.
NOTE: Non-professional mechanics should take note that since DPF regeneration systems vary greatly between applications and even between models in a particular model range, diagnosing DPF issues typically requires the use of manufacturer specific software and equipment. Also, note that repair options are almost always make and model specific and furthermore, that specific, targeted diagnostic tests need to be run to diagnoses most DPF issues accurately. For these reasons, non-professional mechanics are strongly urged to refer DPF issues to the dealer or other competent repair facilities for professional diagnosis and repair.
Where is the P200D sensor located?
While DPF filters are always located in the exhaust system, the actual location of diesel particulate filters is largely dependent on the make and model, as well as on the type of regeneration system that is used on any given application. Note that for this reason, the image above of a typical diesel exhaust system that incorporates a DPF filter is intended for general informational purposes only. This image only shows the DPF in relation to other major components of the DPF system, and does NOT represent the actual layout of an actual DPF system.
Be aware therefore that some components shown here may not be present on all applications, and some applications may have components that are not shown here. Thus, it is vitally important that the manual for the effected application always be consulted to locate and identify exhaust system parts and/or components correctly.
What are the common causes of code P200D?
Due to the large number of different DPF systems in use today, the possible causes of DPF issues on all applications are far too numerous to list here. However, some causes are common to most, if not all applications, and these could include the following-
- Damaged, shorted, burnt, disconnected, or corroded wiring and/or connectors in the DPF control circuit
- Extended periods of low speed driving in an urban environment. Note though that a forced regeneration will usually (but not always) restore the DPF filter’s efficiency.
- Defective/clogged DPF filter. Note that this is common on high-mileage vehicles, since the older a DPF gets, the more difficult it is to regenerate.
- Defective exhaust temperature sensors
- Defective exhaust backpressure sensors
- Excessive oil consumption. Typical causes of high oil consumption include, but are not limited to, damaged/worn turbo chargers, worn piston rings, and the use of low quality, incorrect or unsuitable engine oil
- Engine misfires that allow excessive amounts of oil to enter the exhaust system
- Use of poor quality fuel
- Excessive fuel pressure
- Use of high concentrations of biodiesel that create higher levels of particulate matter
- Engine vacuum leaks
- Defects and malfunctions in the reductant injection system on applications that use chemical catalysts
- Contaminated reductant fluid, which usually requires replacement of the entire reductant injection system
- Failed or failing PCM. Note that this is a rare event, and the fault must therefore be sought elsewhere before any control module is replaced
WARNING: Be aware that ANY unauthorized modification(s) to the exhaust or engine management system has the potential to cause severe, repeated, recurrent, and/or persistent DPF issues that may be impossible to resolve until and unless the modifications are either removed, or the application’s management systems have been restored to their original settings. Also, note that making unauthorized modifications to the exhaust and other engine management systems is considered as “tampering”, which is a federal offence.
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