2003 Test Groups: 3BMXV03.2S54 & 3BMXV04.9S62
WARNING: This page does not describe the selected car, but rather 14 other vehicles, including the 2003 BMW Z8, 2003 BMW Z4, 2003 BMW X5, 2003 BMW M5, and 2003 BMW M3. However, it is still accessible from the selected car via links, so may be relevant.
- Oxygen Sensor Monitoring (General Description) - Both oxygen sensors upstream from catalyst are separately monitored for rich and lean voltage and response time (period monitoring and jump period monitoring). See Figure and Fig 1 .
- Time Period Of Upstream Oxygen Sensor 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 of the times lambda exceed thresholds which depend on engine speed and load. See Fig 2-Fig 3 .
- Monitoring procedure of downstream oxygen sensors:
- Monitoring From Rich To Lean Intake Mixture - Lean sensor voltage is used to diagnose sensor activity. Therefore, this check is performed during a 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 From 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 functional 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 of electrical faults of sensors upstream and downstream of catalyst (not 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.
- If there is no plausible course of sensor voltage, an open circuit of sensor upstream catalyst can be detected if voltage remains in a specified range after sensor has been heated.