Oil level sensors

When an oil level sensor is faulty, the oil warning indicator light comes on randomly or remains on even when the oil level is correct. Or conversely, the sensor does not indicate that the oil level is too low, even if the engine is running low on oil. The oil indicator light may also intermittently turn on and off, with no link to any real fluctuation in the oil level. In addition to the oil warning, other errors may appear on the on-board computer, linked to the electronic management of the engine. Unusual and excessive oil consumption may appear regularly due to frequent or erroneous warnings from the sensor. In some vehicles, a faulty sensor may prevent the engine from starting up, or it may force the vehicle to switch to safety mode to avoid potential damage. A specific error message may appear on the on-board computer, indicating an issue with the oil level sensor or an issue reading this sensor.

Firstly, we strongly recommend that you check the oil level manually, using the dipstick.

You can also visually inspect the oil level sensor, as well as its connections, in order to determine whether there is any visible damage (corrosion, severed cables, or signs of wear). The sensor is fitted on or near the oil sump.

Secondly, we recommend that you check the electrical continuity of the sensor. To do this, connect a multimeter between the terminals of the sensor and the connections to the electronic system. A lack of continuity could indicate an issue with the wiring.

We also suggest that you check the resistance of the sensor to see whether it is operating within the normal ranges. Using a multimeter, measure the resistance of the sensor with the oil at different levels. The resistance should vary according to the oil level. If the resistance remains constant or does not change accordingly, this may indicate that the sensor is faulty.

If this is not sufficient, we recommend that you go to a professional, so that they can use an OBD-II diagnostic tool to reveal the fault codes associated with the oil level sensor. For example, a code such as P250F (Low Engine Oil Level Sensor Circuit) may indicate issues with the sensor.

If the preceding tests are inconclusive, then it would appear that you will need to replace your vehicle’s oil level sensor.

Like any mechanical or electronic part, the oil level sensor can wear out over time, losing accuracy or stopping working completely. As a result, the sensor may send incorrect information or no longer work at all. Over time, engine oil can become clogged up due to dust, combustion residue, and other impurities. The sensor may be damaged by excessive impacts or vibration, particularly if it is incorrectly fixed or is exposed to considerable engine movement. The electrical or metallic components of the sensor may be affected by corrosion, especially if the vehicle is used in humid or salty environments. Corrosion of electrical connections is a frequent cause of failure. The cables or connectors linking the oil level sensor to the on-board computer may become damaged, loosened, or corroded. This can be caused by vibration, incorrect assembly, or exposure to high temperatures. The sensor itself may suffer from internal electronic failure. Electronic components can be sensitive to power surges, temperature variations, or simply manufacturing faults. Excessive engine overheating can affect the sensor, especially if it is located near the hottest areas of the engine. The use of poor-quality, contaminated, or excessively viscous oil may affect the operation of the sensor. An incorrectly installed or fitted sensor, whether original equipment or after a repair, can cause malfunctions. If the sensor is not correctly positioned, it may not measure the oil level accurately. In some cases, poor sensor performance may be due to a software issue in the electronic control unit (ECU). Obsolete or faulty software may incorrectly interpret the signals from the sensor.

We recommend that you follow the steps below to replace your oil level sensor as efficiently as possible and to minimize the risk of any error:

1. 1. Disconnect the vehicle battery’s negative terminal.
   2. Locate the oil level sensor, which is usually located on or near the oil sump, under the engine.
   3. Disconnect the cable harness connected to the sensor. This is usually done by pressing a security clip or latch. Carefully remove the electrical connection.
   4. Depending on the engine design, drain some or all of the engine oil to prevent any oil spillage when the sensor is extracted.
   5. Remove the oil level sensor using a wrench or socket to unscrew the bolts or screws holding the sensor in place.
   6. Place the new sensor in the housing of the previous sensor. Make sure that the new sensor has been supplied with a new gasket to guarantee the sealing.
   7. Reconnect the cables to the new sensor.
   8. Top up the oil (if it was drained during one of the previous steps).
   9. Reconnect the vehicle’s battery.
   10. Make sure that no dashboard indicator lights come on, and that there are no oil leaks in the area around the sensor.
   11. If necessary, reinitialize the on-board computer using an OBD-II tool, to avoid any display errors or incorrect warnings.

As the oil level sensor is essential to the correct operation of the engine, it is important to follow certain advice in order to prolong its service life:

• Replace the gasket in order to mitigate oil leaks and the infiltration of dirt or contaminants into the system;
• Tighten the fixings to the correct torque;
• Avoid impacts when fitting the sensor;
• Change the oil regularly, using a high-quality grade of oil.