2002 Test Groups: 2BMXV03.0LER, 2BMXV03.0M5R & 2BMXT03.0E5R

WARNING: This page does not describe the selected car, but rather 18 other vehicles, including the 2002 BMW Z8, 2002 BMW Z3, 2002 BMW X5, 2002 BMW M5, and 2002 BMW M3. However, it is still accessible from the selected car via links, so may be relevant.

General Description Of Upstream Oxygen Sensor Monitoring - Both oxygen sensors upstream from catalyst are separately monitored for rich and lean voltage and response time (period monitoring and jump period monitoring). See Fig 1.

Fig 1: Oxygen Sensor Monitoring
Courtesy of BMW OF NORTH AMERICA, INC.
Upstream Oxygen Sensor Monitoring Procedure - To determine switching time, lean and rich period times are added during a fixed number of lambda controller cycles. A malfunction is registered if one or both times exceed thresholds which depend on engine speed and load. See Fig 2.

Fig 2: Flow Chart Of Monitoring Oxygen Sensor Switching Time (Lean To Rich)
Courtesy of BMW OF NORTH AMERICA, INC.
Monitoring Of Downstream Oxygen Sensors - Activity of monitor sensor after reaching operating conditions, is determined by an oscillation check of sensor signal (voltage). If conditions of following checks are fulfilled, monitor sensor is regarded to be in order. If monitor sensor detected a defect in these checks, a fault code is stored and MIL is illuminated at next driving cycle:
- Monitor sensor signal (sensor voltage) is greater or equal than a predetermined value at normal engine operating condition (normal combustion).
- Sensor voltage drops below a predetermined value during fuel cut-off conditions.
Oxygen Sensor Heater Monitoring - For proper function of the oxygen sensor, sensor element must be heated. A non-functioning heater delays sensor readiness for closed loop control and influences emissions. Monitoring function measures continuously both sensor heater current as well as heater voltage (heater supply voltage) to calculate sensor heater resistance. See Fig 3.

Fig 3: Heater Control & Heater Current Circuit
Courtesy of BMW OF NORTH AMERICA, INC.
Oxygen Sensor Circuit Monitoring - System monitors electrical faults of sensors upstream and downstream of catalyst:
- Not plausible voltages:
  1. Voltages exceeding maximum threshold are caused by a short circuit to voltage.
  2. Voltages falling below minimum threshold are caused by a short circuit of sensor signal or sensor ground to PCM ground.
    - Not plausible course of sensor voltage: An open circuit of sensor upstream catalyst can be detected if voltage is remaining in a specified range after sensor has been heated. See Fig 4.
      
      Fig 4: Oxygen Sensor Heater Monitoring Flow Chart
      Courtesy of BMW OF NORTH AMERICA, INC.