The Diesel Particulate Filter (DPF) located in the exhaust system is 98% effective in removing soot. It creates slight back pressure and its functionality is monitored by the PCM (Powertrain Control Module) through feedback sensors. These filters have regenerative capacity and allow burn the soot accumulation.
When the diagnostic code P2002 OBDII is stored, it is because of a problem that was found in the DPF filter. This is because the signal sent by the backpressure sensor to the PCM is not within the established parameters. The PCM understands this as a defect in the filter, so it will activate this code along with the Check Engine light.