ENGINE | 646 in MODEL 909 |
D18.40-1102-08
B40/5 | Engine oil level sensor |
Location
The engine oil level sensor is located on the oil pan.
Task
To warn the driver through a display in the instrument cluster (P15) that the oil level is too high or too low.
Determine the oil temperature.
To detect the oil quality for an oil change interval display according to demand.
Function
The oil level, oil temperature and oil quality are detected by means of the engine oil level sensor installed in the oil pan. The sensor operates in accordance with the capacitive measuring principle and features integrated electronics which analyze the three signals. This information is continuously transmitted over a pulse width modulations (PWM) signal to the CDI control unit (N3/21).
The CDI control unit transmits the respective information as the messages "T_OEL (oil temperature)", "OEL_FS (oil level)" and "OEL_QUAL (oil quality)" via the engine CAN (CAN C) to the IC. Each information block consists of three successive square wave signals. This is followed by a short pause. A measured quantity is assigned to each square wave signal. Establishment of the size in each case is based on the duty cycle of approx. 20 to 80%.
The oil quality is measured for the demand-based oil change interval display. The oil quality is detected on the basis of the capacitance of the engine oil (dielectric), this being as much as 6 times greater if the oil quality is poor.
The measuring range for the oil level is 80 mm with a measurement accuracy of about 3 mm. Oil level and oil quality (capacitance of the engine oil) are interdependent. The information is first calculated in the CDI control unit before being transmitted via the engine CAN. Faults at the engine oil level sensor are detected by the CDI control unit and entered in the fault memory. The power supply (approx. 5 V) for the engine oil level sensor takes place by the CDI control unit.