Symptoms and Severity
Since DPF regeneration is essential to maintain the desired exhaust backpressure, addressing a P2459 should be considered a priority. Symptoms of a P2459 code may include:
- Excessive black smoke from the exhaust
- Other DPF codes usually accompany P2459
- Inability to maintain RPM
- Increased engine temperature
- Overheated DPF housing or other exhaust components
The potential causes for setting this code are as follows:
- Faulty DPF pressure sensor
- Faulty exhaust pressure sensor
- Insufficient diesel exhaust fluid
- Incorrect diesel exhaust fluid
- Shorted or open wiring to the DPF injection system
- Faulty PCM or PCM programming error
Diagnostic and Repair Procedures
A good starting point is always to check the technical service bulletins (TSB) for your specific vehicle. Your issue may be a known problem with a known fix published by the manufacturer and can save you time and money during diagnosis.
To diagnose a P2459, a vehicle service manual (or equivalent), a scanner, and a digital volt/ohmmeter will be required.
I like to start by inspecting all cable harnesses and connectors related to the system. I’ve found that this saves me time later, especially if I pay close attention to harnesses located near hot exhaust pipes and manifolds. Now is the time to test the battery load, check battery terminal ends, battery cables, and alternator output.
Now, connect the scanner to the diagnostic port and retrieve all stored fault codes and freeze frame data. Note this information before clearing the codes and testing the vehicle. This can be very helpful later. Test the level and quality of the diesel exhaust fluid and activate the DPF regeneration system if the code does not reset immediately after the road test. If the regeneration procedure was inadvertently interrupted due to another uncorrected issue that has been fixed, the regeneration process can be completed (in the correct increments) at this time.
Follow the manufacturer’s recommendations for testing the DPF pressure sensor (with the DVOM) if the code does not reset immediately. If the sensor does not meet the manufacturer’s resistance specifications, it should be replaced.
Additional Diagnostic Notes:
- Incorrect/insufficient diesel exhaust fluid is a common cause of DPF regeneration sequence/failure frequency codes
- Diagnose and repair DPF pressure sensor codes before attempting to diagnose this code
- Clogged/collapsed DPF pressure sensor hoses/lines are common