Test Group VBM4.4VJGFEK & VBM5.4V8GFEK
WARNING: This page does not describe the selected car, but rather 13 other vehicles, including the 1997 BMW Z3, 1997 BMW 850Ci, 1997 BMW 840Ci, 1997 BMW 750iL, and 1997 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.