Light-Off Temperature Shift for Catalyzed Diesel Particulate Filter On-Board Diagnostics 2012-01-1248

Upcoming California on-board diagnostics (OBD) regulations require lighting the malfunction indicator lamp (MIL) when a catalyzed diesel particulate filter (CDPF) is inert with respect to nonmethane hydrocarbon (NMHC). Light-off temperature shift detection uses a correlation between CDPF age and the gradual increase in catalyst light-off temperature to determine the age of a CDPF. The proposed OBD strategy necessitates slipping HC past the upstream diesel oxidation catalyst (DOC) to ignite on the CDPF. The best-case OBD solution space requires engine net power levels less than 43 hp on a Cummins ISB. Radial temperature measurements downstream of the DOC revealed regional DOC light-off which would not be able to be detected by a single temperature sensor. CDPF light-off independent of DOC light-off was never observed under any testing, eliminating the possibility of using light-off temperature shift as a detection strategy.