P2463 – Diesel Particulate Filter Restriction – Soot Accumulation

What Does Code P2463 Mean?

OBD II fault code P2463 is a generic code that is defined as “Diesel Particulate Filter Restriction – Soot Accumulation”, and is set on all diesel applications when the PCM (Powertrain Control Module) detects an excessive accumulation of solid particulate matter (diesel soot) in the diesel particulate filter. Note that the amount of soot that constitutes an “excessive load” varies between manufacturers and applications on the one hand, and that the volumes of both the diesel particulate filter, and the exhaust system as a whole, play a decisive role in determining the level of backpressure required to initiate a regeneration cycle of the DPF (Diesel Particulate Filter), on the other.

As its name suggests, the function of the DPF is to trap, or filter out the solid particulate matter in diesel exhaust, and to contain the soot until a process of regeneration is initiated to burn off the trapped soot. During this process, the soot is reduced to carbon dioxide, water, and other harmless substances.

We need not delve into the complexities of DPF filter media here, but suffice to say that even the most efficient DPF’s eventually clog up. However, to extend the useful life of a DPF, manufacturers use various processes and technologies to heat the DPF to the point where the soot is combusted. One such technology is to inject fuel into the exhaust upstream of the DPF, which is then ignited. This raises the temperature in the DPF to about 1 200⁰F (650⁰C), at which point the soot is converted into harmless ash, which is then expelled through the tail pipe.

The advantages of this method are that engine performance does not suffer, and that it uses between 30%, and 50% less additional fuel than other methods of DPF regeneration.

One other method involves spraying additional fuel into the combustion chamber while the exhaust valves are open. This enriches the exhaust stream to the point where residual heat ignites the additional fuel, which ultimately has the same effect as the previously discussed method, which is to raise the temperature in the DPF to the point where the soot deposits are incinerated before being expelled.

However, this method has distinct disadvantages, with the most important being that engine performance suffers measurably during the regeneration process. Other disadvantages include the fact that the relatively large volumes of additional fuel dilute the protective oil film on the cylinder walls, and that eventually, some of the additional fuel dilutes the engine oil, thereby reducing the oil’s lubricity.

In a fully functional system, a pressure sensor monitors the pressure in the exhaust both upstream, and downstream of the DPF. As soot collects in the DPF, the pressure upstream of the DPF increases progressively until a pre-programmed minimum threshold is reached, because the flow of exhaust gas is being restricted. At this point, the PCM may, or may not illuminate a service or warning light, depending on the application, but should the regeneration process be delayed, or not initiated, the DPF will become progressively more clogged until the next pre-programmed threshold is reached.

When this happens, the exhaust system can no longer extract the exhaust stream efficiently, because the clogged DPF forms an effective plug in the system. Thus, to prevent potential engine damage caused by the excessive back pressure in the exhaust system, the PCM will set code P2463, and illuminate a warning light. At the same time, the PCM will force the engine into a failsafe, or limp mode, and disable the EGR (Exhaust Gas Recirculation) system to prevent even more soot from collecting in the DPF. On most applications, the fail-safe mode will persist until the problem is resolved.

The image below shows the basic operating principles of a typical DPF, in which heat is used to convert collected soot into harmless ash. This process constitutes the “regeneration”, or “cleaning out” process that restores the DPF’s ability to trap and contain particulate matter in diesel exhaust until the next regeneration process is initiated.

What are the common causes of code P2463?

Common causes of code P2463 could include the following-

• Defective DPF pressure sensor, or collapsed, damaged, and clogged pressure hoses
• Damaged, burnt, shorted, disconnected, or corroded wiring and/or connectors
• Clogged DPF
• On applications with SCR (Selective Catalytic Reduction) systems, almost any problem related to the injection system or the diesel exhaust fluid itself can cause inefficient or ineffective regeneration of the DPF, or in some cases, no regeneration of the DPF to take place at all.
• Almost any code that relates to the exhaust temperature being either too low or too high for regeneration of the DPF to take place can contribute to code P2463, or eventually be the direct cause of this code. These codes include P244C, P244D, P244E, and P244F, but note that there may be manufacturer specific codes that relate to the exhaust gas temperature as well.
• The CHECK ENGINE/SERVICE ENGINE warning light is illuminated for any reason
• The EGR (Exhaust Gas Recirculation) valve is defective, or the EGR valve control circuit is defective in any way
• There is less than about 20 liters of fuel in the tank
• Failed or failing PCM. Note that this is a rare event and the fault must be sought elsewhere before any controller is replaced

What are the symptoms of code P2463?

Some common symptoms of code P2463 could include the following-

• Stored trouble code and an illuminated warning light
• In many cases, several additional codes may be present. Note that in some cases, additional codes may not be directly related to the DPF regeneration issue
• Vehicle may enter a fail-safe, or limp mode that will persist until the problem is resolved
• Depending on the application and the exact nature of the problem, some applications may experience a marked loss of power
• Fuel consumption may increase noticeably
• Excessive black smoke from the tail pipe may be present
• In severe cases, the engine temperature may reach abnormally high levels
• In some cases, the entire exhaust system may be hotter than normal
• Indicated oil level may be above the “FULL” mark due to the oil being diluted by fuel. In these cases, the oil will have a distinct diesel-fuel odor
• Other components, such as the EGR valve and its associated tubes may be clogged as well

How do you troubleshoot code P2463?

SPECIAL NOTES: Non-professional mechanics are strongly urged to gain at least a working knowledge of how modern diesel exhaust emission control systems work by studying the relevant section in the manual for the application being worked on, before attempting a diagnosis and/or repair of code P2463.

This is particularly important where the affected application is fitted with a SCR (Selective Catalytic Reduction) system that injects urea, aka, Diesel Exhaust Fluid into the exhaust system to reduce the formation of particulate matter. These systems are not known for their reliability, and many DPF related issues stem directly from malfunctions in, and failures of, the injection system.

Failure to understand how the urea injection system works, or why it is required in the first place, will almost certainly lead to misdiagnoses, wasted time, and quite possibly to the unnecessary replacement of a DPF filter, which costs several thousand dollars. END OF SPECIAL NOTES.

NOTE: Although all DPF filters have reasonably long service lives, this lifetime is nevertheless finite, and can be influenced (reduced) by many factors, such as excessive oil consumption for whatever reason, over fuelling, extended periods of city driving or driving at low speeds, among others. These factors must be taken into account when diagnosing this code; not doing so can lead to frequent recurrences of the code, reduced fuel economy, sustained power loss, and in severe cases, even engine failure caused by excessive backpressure in the exhaust system.

Step 1

Record all fault codes present, as well as all available freeze frame data. This information can be of use should an intermittent fault be diagnosed later on.

NOTE: Code P2463 is frequently accompanied by several other emissions related codes, and particularly if the application is fitted with a Selective Catalytic Reduction system as an addition to the DPF. Many codes related to this system can either cause, or contribute to code P2463 being set, which makes it imperative that all codes relating to the injection system are investigated and resolved before a diagnosis and/or repair of P2463 is attempted. Bear in mind though that in some cases, such as when the diesel fluid had become contaminated, it might be necessary to replace the entire injection system before some codes can be cleared, or before P2463 can be resolved.

In light of the above, non-professional mechanics are advised to always refer to the manual for the application being worked on for detailed information on the emission control system for that application, since manufacturers do not follow a standard, one-size-fits-all approach to diesel exhaust emission control systems, and/or the devices used to control and/or reduce diesel exhaust emissions.

Step 2

Assuming that there are no additional codes present along with P2463, refer to the manual to locate and identify all relevant components, as well as the location, function, color-coding, and routing of all associated wiring and/or hoses.

Step 3

Perform a thorough visual inspection of all associated wiring, and look for damaged, burnt, shorted, or corroded wiring and/or connectors. Repair, or replace wiring as required.

NOTE: Pay particular attention to the DPF filter pressure sensor and its associated wiring/connectors at this time, as well as all hoses/pressure lines leading to the sensor. Clogged, collapsed, or damaged pressure lines is a common cause of this code, so remove all lines and check for blockages and/or damage. Replace all pressure lines and/or connectors that are in a less-than-perfect condition.

Step 4

If no visible damage to wiring and/or pressure lines is found, prepare to perform ground, resistance, continuity, and reference voltage checks on all associated wiring, but be sure to disconnect all relevant wiring from the PCM to prevent damage to the controller during resistance tests.

Pay particular attention to the reference -, and signal voltage circuits. Excessive (or insufficient) resistances in these circuits can cause the PCM to “think” that the pressure differential upstream and downstream of the DPF is either bigger or smaller than it really is, which can cause it to set this code.

Compare all obtained readings with the values stated in the manual, and make repairs, or replace wiring as required to ensure that all electrical values fall within the ranges specified by the manufacturer.

NOTE: Bear in mind that the DPF pressure sensor forms part of the control circuit, and as such, its internal resistance must be checked as well. Replace the sensor if it does not conform to the specified value.

Step 5

If the code persists, but all electrical values conform to specifications, use the scanner to initiate a forced regeneration of the DPF, but be sure to do this only in a well-ventilated area, but preferably in the open air.

The object of this exercise is to verify that the repairs to wiring or the replacement of the DPF pressure sensor had been successful. However, forced regeneration cycles MUST be performed in strict accordance with the instructions provided in the manual both to ensure that the process is initiated, and to ensure that the process completes successfully.

Step 6

Bear in mind that if the regeneration does not initiate, it could be due to the following reasons-

• The CHECK ENGINE/SERVICE ENGINE warning light is illuminated for any reason
• The EGR (Exhaust Gas Recirculation) valve is defective, or the EGR valve control circuit is defective in any way
• There is less than about 20 liters of fuel in the tank

If the regeneration process does not initiate, make sure that the above conditions are met before condemning either the DPF or the PCM.

Step 7

If the regeneration process does initiate, monitor the process on the scanner and pay particular attention to the pressure upstream of the DPF as indicated by the scanner. The actual pressure depends on the application, but it should not approach the maximum allowable limit at any time during the process. Refer to the manual for details on the maximum allowable pressure upstream of the DPF for that particular application.

If the upstream pressure does approach the prescribed limit, and the DPF has been in service for about 75 000 miles or thereabouts, it is likely that the DPF had reached the end of its useful life. While a forced regeneration might resolve code P2463 temporarily, it is likely that the problem will recur fairly soon, and well within (or several times within) the 300 mile or so interval between automatic regeneration cycles, at that.

Step 8

It should be borne in mind that stock, or OEM diesel particulate filters cannot be serviced, or “cleaned out” in ways that will restore its effectiveness to the level of a new unit, despite the claims made by many so-called experts.

The DPF is an integral part of the exhaust emission control system, and the only reliable way to ensure that the entire system functions at its peak, is to replace the DPF either with an OEM part, or with one of the many excellent aftermarket units that are designed to be serviceable. However, all DPF replacements require that the PCM be adapted to recognize the replacement DPF.

While the adaptation process can sometimes be done successfully on a DIY basis by following the instructions provided in the manual, this procedure is generally best left to the authorized dealers, or other specialist repair shops who have access to suitable equipment and the latest software updates.