Symptoms
and severity
The conditions that may trigger this code can also cause internal damage to the engine or fuel system and should be considered urgent. Symptoms of a P2456 code may include:
- Reduced engine performance
- Excessive black smoke from the engine exhaust
- An increase in engine temperatures
Causes
Causes
potential for setting this code are as follows:
- Exhaust leaks
- Open/short circuit(s) in the DPF pressure sensor A circuit
- Faulty DPF pressure sensor
- Clogged, cracked, or collapsed DPF pressure sensor tubes/pipes
- Empty diesel exhaust fluid tank
- Incorrect diesel exhaust fluid
Diagnostic and Repair Procedures
A good starting point is always to check the technical service bulletins (TSBs) for your specific vehicle. Your issue may be a known problem with a known fix released by the manufacturer and can save you time and money when diagnosing.
To properly diagnose a P2456, I need a digital volt/ohmmeter, a manufacturer’s service manual, and a diagnostic scanner.
I would begin my diagnosis with a visual inspection of the related wiring harnesses and connectors. I would inspect the wiring routed near hot exhaust components and/or sharp edges. This saves time if I am certain to check the alternator output, battery voltage, and battery terminal ends at this time.
My next step would be to connect the scanner and retrieve all stored codes and freeze frame data. I would write down this information for future reference and then clear all stored codes.
Using the DVOM, I would follow the manufacturer’s recommendations for testing the DPF pressure sensor. I would consult the service manual for specific instructions. Sensors that do not meet the manufacturer’s resistance specifications should be replaced.
If the sensor checks out, I would continue by checking the DPF pressure sensor supply tubes for obstructions and/or damage. I would replace tubes that are burned, cracked, or collapsed (high-temperature silicone tubes are recommended).
If the supply sensor lines are intact and the sensor is operational, I would proceed by testing the system circuits. To avoid damaging the PCM, I always disconnect the related controllers before testing resistance and/or continuity with the DVOM.
Additional Diagnostic Notes:
- The DPF regeneration fluid must be checked before diagnosing this code
- When P2456 is stored, I have found that clogged sensor ports and clogged sensor tubes are common
- DPF pressure sensor tubes that have melted or been cut may need to be rerouted after replacement