OBD-II Diagnostics
Malfunction Indicator Light (MIL) can be diagnosed with an aftermarket scan tool that allows technicians without BMW special tools or equipment to diagnose an emission system failure. With the use of a universal scan tool connected to Data Link Connector (DLC), an SAE standardized DTC can be obtained, along with condition associated with the illumination of MIL. If using a BMW scan tool, a fault code and the conditions associated with its setting can be obtained prior to the illumination of the MIL.
OBD-II Diagnostic Trouble Codes (DTC) are designed to be identified by their alpha/numeric structure. DTCs start with letter "P" for powertrain related systems. See Fig 1. DTCs are stored whenever the Check Engine Light (MIL) is illuminated. Universal diagnostic access to DTCs is via a standardized Diagnostic Link Connector (DLC) using a standardized tester (scan tool). DTCs only provide one set of environmental operating conditions when a fault is stored. This single freeze frame refers to vehicles environmental conditions for a specific time when fault first occurred. Information which is stored is limited in scope. This information may not even be specific to type of fault. See TEST GROUP IDENTIFICATION . On BMW, OBD-II monitors following systems:
- Catalyst Monitoring.
- Misfire Monitoring.
- Evaporative (EVAP) System Monitoring.
- Secondary Air System Monitoring.
- Fuel System Monitoring.
- Oxygen Sensor Monitoring.