Test Groups WBMXV04.4M62 & WBMXV05.4M73
WARNING: This page does not describe the selected car, but rather 14 other vehicles, including the 1998 BMW Z3, 1998 BMW M3, 1998 BMW M Roadster, 1998 BMW 750iL, and 1998 BMW 740iL. 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 the catalyst are separately monitored for rich and lean voltage and response time (period monitoring and jump period monitoring).
- Monitoring Structure - See Figure.
- Flow Chart Of Monitoring Function - See Fig 1.
- Oxygen Sensor Heater Monitoring - For proper function of the oxygen sensor, the sensor element must be heated. A non functioning heater delays the sensor readiness for closed loop control and influences emissions. The monitoring function measures both, sensor heater current (voltage drop over a shunt) and the heater voltage (heater supply voltage) to calculate sensor heater resistance. The monitoring function is activated once per trip, once the heater has been switched on for a certain time period and the current has stabilized. For flow chart of monitoring function of oxygen sensor heating, see Figure.
- Flow Chart Of Oxygen Sensor Heater Monitoring Function - See Figure.
- Oxygen Sensor Circuit Monitoring -
Monitoring of electrical faults of sensors upstream and downstream of catalyst, consists of following:
- Unplausible Voltages - ADC voltages exceeding the maximum threshold VMAX are caused by a short circuit to battery voltage, or ADC voltages falling below the minimum threshold VMIN are caused by a short circuit of sensor signal or sensor ground to ECM ground.
- Unplausible Course Of Sensor Voltage - An open circuit of the sensor upstream catalyst can be detected, if the ADC voltage remains in a specified range after the sensor has been heated.