7-Series (V8)
- Sensor conductivity is efficient when the oxygen sensor is hot 1382°F (750°C). For this reason, sensor contains a heating element. This reduces warm up time and retains heat during low engine speed when exhaust temperature is cooler. Oxygen sensor heating elements receive power from Integrated Voltage Supply Module (IVM) and ground supply is pulse width modulated by the ECM. Monitored voltage signal is constantly changing due to combustion variations and normal exhaust pulsations. At a value of lambda = 1, pump cell requires approximately 3 milliamps. Oxygen sensor signal voltage is approximately 1.5 volts. Reference cell voltage is approximately 450 millivolts. At a lambda value of less than one (rich), oxygen sensor signal voltage is approximately.3 volt. At a lambda value of greater than one (lean), oxygen sensor signal voltage is approximately 4.3 volts.
- If necessary, ECM will correct air/fuel ratio by regulating injection time. ECM monitors length of time sensors are operating in lean, rich and rest conditions. Evaluation period of sensors is over a predefined number of oscillation cycles and pump cell amperage.