When the oil pressure begins to rise, the oil pressure sensor contact is activated in the engine. The current circuit opens. The control lamp goes out. Cold engine oil is quite viscous. This causes a high oil pressure, so the control lamp goes out already when the engine is started or after that. In a hot summer, in a hot running engine, the oil is very thin (low viscosity). Because of this, his pressure, respectively. becomes lower; the control lamp goes out only at higher speeds.
The illustration shows the left front side near the cylinder head of a diesel "Volkswagen": 1 - temperature sensor; 2 - oil pressure sensor; 3 - engine temperature sensor; To determine the required pre-glow time, the sensor gives a signal to the pre-glow relay.
Faults
If the oil pressure warning light flashes suddenly while driving, it is dangerous to the engine.
If it lights up briefly during heavy braking or fast driving on a curved track, the oil level has obviously dropped below the minimum mark. Check the level, add oil if necessary.
If the light stays on for a long time, stop the car immediately!
Then, first of all, check if the blue-black wire from the oil pressure sensor to the LED has a short circuit. Turn on the ignition, remove the wire from the oil pressure sensor. The control lamp should go out when the engine is off. It is best to have an assistant supervise. If it continues to burn further, then the wire is rubbed somewhere and has a contact "to ground". This will not cause damage to the engine; you can go further.
However, usually when the oil pressure warning light comes on, it indicates that there is not enough pressure in the engine lubrication points. In most cases, this is not caused by a defect in the oil pump, but most often by a sudden loss of oil. For example, the drain plug is loose. If the malfunction endangers the engine, the vehicle must be towed.
If the oil pressure indicator light is constantly on, then the cause is often a defective sensor. But only by replacing the sensor can this really be established.
When the ignition key is turned on, the oil pressure light does not come on. Turn on the ignition, remove the wire from the oil pressure sensor and press it against "mass"; if the lamp is now on, then there is a malfunction in the oil pressure sensor. Replace sensor. If the bulb does not light, then the defect is in the power wire, in the lamp itself or in the LED.
Instruction. In the event that the oil pressure warning light flashes after driving through a large puddle of water, in most cases this is caused by the following reason. The oil pump is driven by an intermediate shaft, which in turn is driven by the smooth back of the toothed belt. If the tension of the toothed belt is too loose, it has become oily or, for example, water has entered this drive, the toothed belt slips briefly on the intermediate shaft. And as a result, too little oil is supplied. It is urgent to check the tension of the toothed belt and its condition. See chapter "Engine".
Oil pressure sensor replacement
The oil pressure sensor is located in an accessible location on the left side of the cylinder head (looking in the direction of travel)
When replacing the sensor, screw it in with a new sealing ring. The torque is 25 Nm.
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