Self-Diagnostic System: Notes

ECM is equipped with On Board Diagnostics-II (OBD-II) system which monitors emission related components and systems for malfunction or deterioration. When OBD-II determines there is an emissions related problem, the Malfunction Indicator Light (MIL) is illuminated and ECM stores a Diagnostic Trouble Code (DTC).

ECM programming includes advanced diagnostic test modes 6, 7 and 22. Mode 6 allows access to catalyst and evaporative systems test results which are not continuously monitored by ECM. Mode 7 allows off-board testing of emission related devices that are continuously monitored by ECM. Mode 7 also enables verification of repair in only one drive cycle and without having to duplicate particular operating conditions. Mode 22 allows accessing PIDs (inputs and outputs). For further information, see appropriate SELF-DIAGNOSTICS article.