Component description for the oil sensor

P18.40-2086-01

Locations

B40 Oil sensor (oil level, temperature and quality)

The oil sensor is located at transmission end below in the engine oil pan.

Task

The oil sensor detects:

 Oil level

 Oil temperature

 Oil quality (for demand-based oil change interval display)

P18.40-2105-11

Design

1 Integrated electronics

B40 Oil sensor (oil level, temperature and quality)

a Capacitive measuring range

C 3-pin connection

Pin 1: output signal (PWM signal)

Pin 2: GND

Pin 3: Voltage supply (5 V)

P07.61-0445-05

Oil sensor signal assignment

1 Signal duty cycle OK

A Oil temperature 20 to 80%

B Oil level 20 to 80%

C Oil quality 20 to 80%

2 Signal duty cycle >80 %

A Oil temperature >+160 °C

B Oil level >80 mm

C Oil quality good

3 Signal duty cycle <20%

A Oil temperature <- 40°C

B Oil level <0 mm

C Oil quality poor

T pulse duty factor 100%

Function

The oil sensor operates in accordance with the capacitive measuring principle and features integrated electronics which analyze the three signals (oil level, temperature and quality).

The information is sent constantly by means of a pulse width modulated signal (PWM signal) to the CDI control unit (N3/9) and then via the CAN databus to the instrument cluster (A1).

Each information block consists of three successive square-wave signals, This is followed by a short pause.

A measured variable is assigned to each square-wave signal (A, B, C). The quantisizing in each case is based on the on/off ratio (T) of approx. 20 to 80 %.

The voltage for the oil sensor (approx. 5 V) is supplied by the CDI control unit.

Oil level and oil quality are detected on the basis of the capacitance of the engine oil (dielectric).

The capacitance of the engine oil is as much as 6 times greater if the oil quality is poor.

The measuring range for the oil level is 80 mm (normal level
 40 mm) with a measuring accuracy of about  3 mm.

The oil temperature is detected by the temperature sensor.

All the signals are processed in the integrated electronics in the oil sensor to form a PWM signal and passed on to the CDI control unit.

Oil level and oil quality (capacitance of the engine oil) are interdependent. For this reason this information is not compensated until it reaches the CDI control unit before being transmitted via CAN databus.



Faults at the oil sensor are detected by the CDI control unit and entered in the fault memory.