Oil condition sensor
The oil condition sensor increases the function range of the thermal oil level sensor. The oil condition sensor measures the following variables:
- Engine oil temperature
- Oil level
- Dielectric conductivity.
The Digital Engine Electronics (DME) evaluate these measured variables. With the oil condition sensor, the electrical properties of the engine oil are also determined. The characteristics change with wear of the engine as well as changes to the engine oil (for example, ageing, deposits).
The oil condition sensor is attached to the oil sump and is accessible from below. There is no longer an oil dipstick. Electronic oil-level monitoring is now a feature of all engines.
The oil condition sensor consists of 2 cylindrical condensers. The condensers are mounted above one another. 2 metal tubes are inserted one into the other to serve as electrodes. The engine oil is used as a dielectric medium between the electrodes.
| Index | Explanation |
|---|---|
| 1 | Measuring tube for detecting level |
| 2 | Temperature sensor |
| 3 | Three-pin plug connection |
The temperature sensor is seated on the housing of the oil condition sensor. The housing of the oil condition sensor contains an electronic evaluation unit. The electronic evaluation unit has self-diagnosis. A fault in the oil condition sensor is entered in the fault memory of the Digital Engine Electronics (DME).
The electrical material properties of the engine oil change as the engine oil wears and ages. The changed electrical properties of the engine oil change the capacitance of the capacitor.
The oil level is measured for the electronic oil level check. The 2nd capacitor in the upper part of the oil condition sensor registers the oil level with the engine running. The capacitor is at the same level as the oil level in the oil sump. As the oil level changes, the capacitance of the capacitor changes. The evaluation electronics unit converts the measured capacity into a digital signal. The Digital Engine Electronics (DME) uses this to calculate the oil level. The electronic oil level check is displayed on the Central Information Display (CID) as well as in the instrument panel (KOMBI). On vehicles without a Central Information Display (CID), the oil level is displayed exclusively in the instrument panel (KOMBI).