Sensor, Oil Level
The engine does not have a conventional "mechanical" dipstick. Instead, the engine has an "electronic dipstick", i.e. an electric sensor. The sensor's measuring body consists of a wire made of an alloy consisting of iron, nickel and cobalt. This gives properties such as small expansion due to heat and little corrosion. The wire is placed in the sensor housing and is held in tension by a spring at the top. The measurement range of the sensor is 65 mm.
The image shows the measurement principle where different measurement ranges can be used for different information to the driver.
The principle is to close the circuit of the sensor for a short period. The oil's cooling effect affects the measurement wire's resistance. The higher the oil level, the greater the cooling effect. Level control occurs by means of the engine control module (ECM) applying a constant voltage of approx. 8V for a short period, approx. 750 ms. As the power supply to the measurement wire is constant, the current will vary depending on the sensor resistance. The current produces a corresponding voltage drop on a resistor connected in series with the measurement wire. The resistor is located in the engine control module (ECM). The voltage across the wire is registered at the beginning and end of the measurement. The difference in voltage corresponds to a certain level. When the oil level is low, the voltage difference is comparatively larger.
Measurement is carried out once per driving cycle, at the start of the driving cycle. The engine must be off for a certain amount of time to obtain the correct measurement result, i.e. nearly all of the oil must have run back to the oil pan.
The combined instrument panel (DIM) informs the driver about the current level and any action required via a graph and text message before the engine is started. See the owner's manual for further information. If the conditions for the measurement are not met, e.g. if the oil temperature has been too low, the tilt angle too large or the engine has not been switched off for long enough then the message "Not available" will appear.