Technical Description of OBD-II Trouble Code
Intermittent Circuit Issue with Diesel Particulate Filter Pressure Sensor A
What does that signify?
This diagnostic trouble code (DTC) is a generic powertrain code that is applicable to all vehicles manufactured from 1996 onwards (Ford, Dodge, GMC, Chevrolet, Mercedes, VW, etc.). While it is a generic code, the specific repair steps may vary depending on the make and model of the vehicle.
If a P2456 code is stored, it means that the powertrain control module (PCM) has detected an erratic or intermittent voltage input signal from the circuit of the diesel particulate filter (DPF) pressure sensor known as A. This code is only used in diesel-equipped vehicles.
DPF systems are designed to remove around ninety percent of carbon particles (soot) from the exhaust of diesel engines. The DPF element traps larger soot particles while allowing smaller particles and other exhaust gas compounds to flow through.
The filtration element is at the core of the DPF. Some of the elemental compounds used in DPF construction include paper fibers, metal fibers, ceramic fibers, silicone wall fibers, and cordierite wall fibers. Ceramic-based cordierite is the most common due to its excellent filtration capabilities. However, it is prone to overheating at higher temperatures, making it vulnerable in vehicles equipped with passive DPF systems. Large soot particles should be trapped between the fibers while engine exhaust is allowed to flow through. When there is a high concentration of soot particles in the element, exhaust pressure increases.
The filtration element needs to be regenerated once the soot concentration reaches a certain level. Regeneration allows exhaust gases to flow through the DPF, maintaining the correct level of exhaust back pressure.
Automatically regenerated systems are known as active DPF systems. In this type of system, the PCM is programmed to inject chemicals such as diesel fuel or diesel exhaust fluid into the exhaust at scheduled intervals. This injection raises the exhaust temperatures, allowing trapped soot particles to be incinerated as ions of nitrogen and oxygen.
Passive DPF systems operate on a similar principle but require input from the operator to activate. On some models, a qualified repair facility will need to perform the regeneration procedure, which can take several hours to complete.
While active regeneration systems work while the vehicle is being driven, passive systems are typically activated when the vehicle is parked.
Once the filtration element is regenerated, exhaust pressure should return to normal levels. The DPF pressure sensor is usually mounted remotely, away from the excessive heat of the DPF. Silicon hoses are used to monitor exhaust back pressure, connecting near the DPF inlet and the DPF pressure sensor. If the PCM detects an intermittent or erratic exhaust pressure condition or an electrical input signal from DPF pressure sensor A, it may store a P2456 code.
Symptoms & Severity
Conditions that could cause this code may also lead to internal engine or fuel system damage and should be considered urgent. Symptoms of a P2456 code may include:
Causes
Potential causes for this code to be set are:
Diagnostic and Repair Procedures
A good starting point is always to check for technical service bulletins (TSB) specific to your vehicle. Your issue may be a known problem with a known solution provided by the manufacturer, which can save you time and money during diagnosis.
To correctly diagnose a P2456 code, you will need a digital volt/ohmmeter, a manufacturer’s service manual, and a diagnostic scanner.
Begin the diagnosis with a visual inspection of related harnesses and connectors. Inspect wiring that is routed near hot exhaust components or jagged edges. It is also important to check alternator output, battery voltage, and battery terminal ends at this time.
Next, connect the scanner and retrieve all stored codes and freeze frame data. Write down this information for future reference and then clear all stored codes.
Using the DVOM, follow the manufacturer’s recommendations for testing the DPF pressure sensor. Consult the service manual for specific instructions. Replace sensors that fail to comply with the manufacturer’s resistance specifications.
If the sensor checks out, continue by checking the DPF pressure sensor supply hoses for clogs or breakage. Replace hoses that are burnt, cracked, or collapsed, and consider using high-temperature silicon hoses.
If the supply sensor lines are intact and the sensor is operational, proceed by testing the system circuits. To prevent PCM damage, always disconnect related controllers before testing resistance and/or continuity with the DVOM.
Additional diagnostic notes:
