Electronic Engine Oil level Sensor
The E38 began production utilizing the electronic oil level sensor, it was later phased into production on other models and engines.
The electronic level sensor is located in the engine sump mounted to the engine oil pan.
The oil level sensor contains an integral microprocessor and two sensing elements. The sensing elements are inside of a plastic shield and are immersed in the oil.
- One element measures the oil temperature.
- The second is heated to 10°C above the temperature of the oil and then switched off to cool.
The length of time it takes to cool the heated element is how the sensor determines the engine oil level. When the oil level is high it covers a larger portion of the probe submersed in the oil sump. The engine oil around the probe cools the heated element faster than if the level is low.
The micro-processor in the base of the sensor supplies a signal to the CCM/LCM with a varying pulse width and frequency.
The "high" or "on" time of the signal is dependent on oil temperature, this means the hotter the oil is, the longer the sensing element has to be heated to reach 10°C above.
The "low" or "off" time of the signal is dependent on the oil level. The lower the oil level is, the longer the "off" time of the signal is.
Cool down times are averaged over a minimum of 350 measurements to take account of slosh in the oil pan while driving. If the average is over the warning limit the low oil warning is set.
Please refer to appropriate article for a table of the warning levels of individual vehicles.