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2003 Test Groups: 3BMXV03.0UL2

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.
  1. Heater Diagnosis Of Upstream Wide-Range Oxygen Sensor (General Description) -  Wide range air fuel ratio sensor is ready for operation at a certain temperature. In most cases, exhaust gas temperature is not sufficient for heating, so electrical heating is needed for cases when exhaust gas temperature is not sufficient for heating, so electrical heating is needed for proper functioning of sensor. Diagnosis consists of 3 checks:
    • Operational Readiness -  Sensor readiness depends on heater performance. Time delay between "heater on" and operational readiness is monitored. Readiness is checked at defined time ranges (dependent on engine coolant temperature) after heater has been switched on.
    • Temperature Check -  A second check is performed continuously. Sensor temperature is expected to remain within a predetermined range. Otherwise heater performance is not sufficient and a fault code is set.
    • Power Stage Diagnosis -  During power stage on and off, control signal (input) of power stage is compared to its limit. With these checks, disconnection as well as short to either ground or battery voltage can be detected, and if appropriate, a fault code is set. See Figure.
  2. Dynamic Diagnosis (Slow Response) -  Dynamic diagnosis runs at same time as catalyst diagnosis (conversion-efficiency) works. During catalyst and oxygen sensor monitoring, model-based nominal amplitude is modified to higher values. This results into an actual amplitude indicated by signal output of the sensor which is averaged over several lambda cycles (leanest A/F ratio minus richest A/F ratio). To enter into the calculation, each measured value has to be within a predefined confidence interval (window). Figure-Figure .
  3. Plausibility Check -  If A/F ratio of upstream sensor is above a predetermined "lean" value and signal of downstream sensor indicates "high" voltage, a fault code is set. If A/F ratio of upstream sensor is below a predetermined "rich" value and signal of downstream sensor indicates "low" voltage, a fault code is set.
  4. Offset Check -  This monitoring looks for an incorrect lambda measurement due to shunting effects. If lambda-offset of downstream-control exceeds a threshold, a fault code is set.
  5. Heater Coupling Check -  Oxygen sensor heater is monitored for low impedance coupling between heater and sensor, which can cause lambda modulations with heater pulse rate. If difference of consecutive lambda values exceeds calibration, a fault code is set.
  6. Monitoring Of Downstream Oxygen Sensors -  After reaching operating conditions, activity of monitor sensor is determined by an oscillation check of sensor signal (voltage). If conditions of following checks are fulfilled, monitor sensor is considered to be functioning properly:
    • Monitor sensor signal (sensor voltage) is greater than or equal to a predetermined value at normal engine operating condition (normal combustion), or sensor voltage drops below a predetermined value during fuel cut-off conditions. If a monitor sensor defect is detected during these checks, a fault code is stored and MIL is illuminated at next driving cycle.
  7. Oxygen Sensor Heater Monitoring (General Description) -  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 continuously measures both sensor heater current as well as heater voltage (heater supply voltage) in order to calculate sensor heater resistance. See Figure-Figure .
  8. Oxygen Sensor Circuit Monitoring (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.
  9. Oxygen Sensor Circuit Monitoring (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.
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