P2002: DPF efficiency is judged from filtered soot-sensor evidence

P2002 is a diesel particulate filter efficiency fault. The reviewed GM row describes a strategy intended to detect a cracked DPF by evaluating soot-sensor information through an exponentially weighted moving-average filter. It is not presented as a simple differential-pressure limit or a direct diagnosis of excess soot loading.

A filtered result needs valid supporting data

The table compares the filtered soot-sensor-current quantity with 11.18, but does not print a unit alongside that threshold. It also changes the filter response according to normal, fast-initial and rapid-response modes. Consequently, a single instantaneous sensor reading cannot be treated as the monitor's final efficiency result.

The diagnostic requires no relevant soot-sensor fault, valid downstream temperature and mass-flow information, and a reliable engine-out soot model. Ambient temperature must exceed −20°C. The continuation also limits auto-stop activity and requires valid EGR-rate information.

What changes the next diagnostic decision

First establish whether the soot measurement and supporting model inputs are valid. A problem that inhibits sensor measurement is not evidence that the filter passed. Then distinguish this efficiency judgment from a pressure-based loading assessment: the source's target is inadequate filtration, so the code alone does not justify a regeneration command.

Verification should confirm completion of the permitted filtered monitor with its prerequisites satisfied. The document lists Type A, one-trip reporting and different response modes, but does not provide a complete service test or prove that the substrate is physically cracked. Exact vehicle, engine and calibration applicability remain to be confirmed beyond this 2025 GM summary.

Source: GM monitor, PDF page 1375; GM monitor, PDF page 1376; GM monitor, PDF page 1377.