2002 Test Groups: 2BMXV03.2S54 & 2BMXV04.9S62
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.
- Monitoring Upstream Oxygen Sensor - Both oxygen sensors upstream from the catalyst are separately monitored for rich and lean voltage and response time (period monitoring and jump period monitoring). 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 Figure.
- Monitoring Structure Of Upstream Oxygen Sensor - See Fig 1.
- Monitoring Procedure Of Upstream Oxygen Sensor - This determines the switching time the lean and rich period times are added during a fixed number of lambda controller cycles. A malfunction is registered if one or both of the times exceed the thresholds which depend on engine speed and load. See Fig 2-Fig 3 .
- Monitoring Procedure Of Downstream Oxygen Sensors (Rich To Lean Intake Mixture) - Lean sensor voltage is used to diagnose sensor activity. Therefore, this check is performed during deceleration fuel cut-off. Diagnosis starts after a calculated air mass (integral) is reached at transient from any operation mode to fuel cut-off mode and a defined time in deceleration fuel cut-off. Sensor voltage has to drop below a predetermined value otherwise a fault is detected and a code is stored.
- Monitoring Procedure Of Downstream Oxygen Sensors (Lean To Rich Intake Mixture) - When diagnostic conditions at deceleration fuel cut-off are not fulfilled, diagnosis is carried out in opposite direction of oxygen sensor voltage. For a positive diagnosis result, signal must overrun a threshold after deceleration fuel cut-off. To ensure diagnosis, mixture can be short-term enriched, independent of respective operating conditions.
- Oxygen Sensor Heater Monitoring - For proper function of 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 Figure-Figure .
- Oxygen Sensor Circuit Monitoring -
Monitoring electrical faults of sensors upstream and downstream of catalyst. Non-plausible voltages:
- Voltages exceeding maximum threshold are caused by a short circuit to voltage.
- Voltages falling below minimum threshold are caused by a short circuit of sensor signal or sensor ground to PCM ground.