P2459: DPF regeneration starts too often relative to modeled soot

P2459 is a regeneration-frequency diagnosis, but this implementation does more than count distance between regenerations. When a qualified regeneration starts, it compares the soot estimate that requested it with the nominal engine-out soot estimate. A large ratio indicates that regenerations are occurring disproportionately to expected soot production.

The trigger matters

The source explicitly distinguishes ranked-soot-model triggers from distance- or time-based regeneration starts. The latter are described as passing this test. It also excludes service requests and certain fault-driven early requests. A previous successful regeneration and valid models over the loading period are relevant prerequisites.

The table offers optional exponentially weighted filtering and different active-fault thresholds. Because the row's threshold and enable layout is difficult to reconcile, this article does not prescribe one universal ratio. Reporting is Type A, one trip, with evaluation at a new regeneration event rather than an arbitrary continuous timer.

Interpreting frequent regeneration

The source lists inefficient combustion, incomplete regeneration, model overestimation and intake or exhaust leakage among detectable mechanisms. It does not rank them or prove which occurred. Preserve the regeneration trigger, previous completion status and both soot estimates. Verification needs another qualified event and a valid comparison; initiating a service regeneration alone does not reproduce the normal frequency monitor.

Source and application limits

This explanation covers the cited 2025 GM monitor. Confirm the vehicle and calibration in its service information before applying these limits; inclusion in this file does not establish model compatibility. GM diagnostic parameters, PDF page 1478. GM diagnostic parameters, PDF page 1479.