|Code||Fault Location||Probable Cause|
|P2454|| Diesel Particulate Filter Pressure Sensor "A" Circuit Low |
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|Wiring, Defective differential pressure sensor, PCM|
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What Does Code P2454 Mean?
OBD II fault code P2454 is a generic code that is defined as “Diesel Particulate Filter Pressure Sensor “A” Circuit Low”, and is set on diesel vehicles when the PCM (Powertrain Control Module) detects an abnormally low voltage in the control and/or signal circuits of the Diesel Particulate Filter Pressure Sensor labelled “A”.
While technologies such as common rail fuel injection and selective catalytic reduction converters have greatly reduced the volume of diesel exhaust emissions that cause smog in urban areas, these technologies cannot eliminate or remove solid particulate matter in diesel exhaust. Commonly known as “soot”, the particulate matter consists of un-combusted hydrocarbon particles that are typically finer than the particles in cigarette smoke.
As a practical matter, the solid particles in diesel exhaust can only trapped in a filter, and later burned off when the soot load in the filter exceeds a critical level, and to do this effectively, engineers and chemists have developed an effective filter that can do just that. In terms of operation, a typical DPF device contains a very fine substrate through which the exhaust gas can flow relatively freely. However, since the device is designed to capture and contain fine particles, the soot will collect and accumulate in the filter until the soot starts to clog up the substrate, raising the pressure in the exhaust system, which is the underlying mechanism that triggers DPF regeneration events.
In terms of operating principles, the PCM uses dedicated pressure sensors to monitor the exhaust backpressure as a means to determine the soot load in the DPF. Thus, when the PCM deems the soot load to be excessive (based on the exhaust backpressure) it will begin a process of regenerating the DPF in one of two ways, depending on the vehicle. One way involves burning off the accumulated soot by raising the exhaust gas temperature, which is typically accomplished by altering the fuel injection timing to allow some combustion to take place in the exhaust manifold.
The other method involves injecting a precisely metered amount of a urea and water mixture (aka ADBlue, or Diesel Exhaust Fluid) into the exhaust system just before the DPF. In a fully functional system, the urea is converted into ammonia, which then acts as a catalyst that initiates the oxidation of the accumulated soot by raising the internal temperature of the DPF to a level where the soot is effectively consumed by the high temperature.
While both systems work very well, the frequency of the rate at which the DPF is regenerated depends both on the way the vehicle is driven, as well as accurate input data from multiple sensors, some of which include exhaust gas temperature sensors, exhaust gas pressure sensors, dedicated NOx sensors, and others. Provided that all inputs are accurate, plausible, and continuous, the PCM will initiate DPF regeneration whenever it deems the soot load to be excessive, without any inputs from the driver.
However, on systems that use a liquid reductant, the regeneration frequency also depends on accurate input data from multiple sensors that monitor the entire reductant injection system. Typical monitoring includes the fluid level in the storage tank, its temperature, the integrity of the injection pump’s wiring and control system(s), and the operation of the reductant metering valve and injection nozzle.
One other factor that comes into play is the mileage driven between regeneration events. While this distance is not fixed, it is factored into both the way the vehicle is driven, and the operating conditions that obtained since the last regeneration event took place. In practice though, all of the requirement and/or enabling conditions described above have to be met, or fulfilled for the PCM to be able to maintain the regeneration frequency of the DPF.
Thus, when a failure or malfunction, such an abnormally low voltage exists in the DPF differential pressure sensor and/or its associated circuits that prevents the frequent regeneration of the DPF, the PCM will set code P2454, illuminate one or more warning lights, and may also initiate a limp mode and/or disable the starting circuit, depending on the vehicle and the exact nature of the problem.
Where is the P2454 sensor located?
The image above is a generic representation of the relative location and operating principles of a typical DPF pressure sensor. As shown here, the sensor monitors the exhaust pressure at both the upstream inlet and downstream outlet of the DPF. In this manner, the sensor is able to determine the pressure difference across the DPF, which serves as the primary input data the PCM uses to determine the soot load, and therefore, the efficiency of the DPF. Thus, when the pressure difference across the DPF cannot be measured accurately due to defect in the pressure sensor’s circuits, the PCM is unable to determine the soot load in the DPF, and therefore, the efficiency of the DPF cannot be determined.
What are the common causes of code P2454?
The causes of code P2454, and indeed, all other DPF related codes are many and varied, but could include one or more of the following-
- Damaged, burnt, shorted, disconnected, and/or corroded wiring and electrical connectors anywhere in the differential pressure sensors’ wiring harness
- Defective differential pressure sensor
- Failed or failing PCM, but note that since is a rare event, the fault must be sought elsewhere before any control module is replaced
What are the symptoms of code P2454?
Common symptoms of code P2454 could include the following, but note that some symptoms of code P2454 and other DPF related codes could immobilize the affected vehicle until the root cause of the code(s) is resolved-
- Stored trouble code(s) and illuminated warning light(s)
- No start condition: note that on some applications, an out-of-range input signal from a defective DPF differential pressure sensor could be interpreted by the PCM as an excessively high soot load in the DPF. In these cases, the PCM may initiate a limp mode, or even disable the engine starting circuits to prevent damage to some components in the exhaust system
- Some vehicles may exhibit varying degrees of power loss, with the severity of this symptom depending on both engine load and speed