P2459: Diesel Particulate Filter Regeneration Frequency

What does P2459 mean?

P2459 means the particulate filter is being regenerated more often than the calibration expects. CARB requires diesel OBD to flag regeneration so frequent that emissions would exceed the limit; frequent regeneration also dilutes oil and costs fuel. Ford's 2023 diesels set it when the average distance between completed regenerations falls below about 40 km. GM's 2014 Cruze 2.0 diesel compares the soot load that triggered a regeneration with a table built from the engine-out soot model, and GM's 2018 diesels flag a ratio of 10 or more between the pressure-based soot estimate and the engine-out model, citing dirty combustion, a leak in the intake or exhaust, or an inefficient filter. The Opel/GM 2.0 CDTi in the Saab 9-5 (2010) instead counts too many interrupted regenerations, as a Type C code. Stellantis replaced the filter on 2022 to 2023 Ram 2500/3500 6.7 Cummins over a manufacturing issue; left alone, the engine eventually derates.

The code tells you which monitor failed, not which part is broken. Test before replacing parts.

Symptoms

• MIL or DPF warning
• Higher fuel consumption and rising oil level
• Reduced engine power if the fault persists

Common causes

• Medium High soot output from the engine (injectors, EGR, air leaks)
• Medium Differential pressure reading too high (sensor, blocked or swapped hoses)
• Low Filter loaded with ash or defective from manufacture

Likelihood is a general estimate across vehicles; your make and model may differ.