Basic automobile, as in transport, had originated in the early years of 1700s. Their sophistication increased in leaps and bounds over time. The heart of any transport vehicle, the engine, was powered by steam in the nascent versions. Development resulted in the use of petrol, diesel, and the likes of a fuel to power the engines.

The rides got smoother and the design of the overall vehicle also turned candid. The globe was no longer unconquerable, with the speed of travel touching the speed of sound and even defeating it as we progressed.

All this, however, necessitated incorporation of multiple sensors within the engine to ensure its correct running.

Oil, inside the vehicle’s engine, is the prime element that lubricates the moving parts of the engine. The cylinder block and the piston head, which move within the cylinder block, are both made up of metal. As they rub against each other, their movements produce kinetic energy in the form of heat, which is needed to move the wheels.

The energy from the burning fuel is converted to kinetic energy by this process. While burning fuel generates its own heat, friction of the moving parts also generates heat, which compares very well to that generated by the burning fuel.

It is necessary and compulsory, therefore, to bring down this rise in temperature. Engine oil is the element that helps us do that. It has two important physical properties: Resistance at warmer temperatures without burning itself and its viscosity. These aid in the cooling and lubricating aspects of the engine internals.

Given the importance of the engine oil, there is a necessity that its quantity within the engine cylinders is monitored and indicated to the user of the engine. In this case, the driver of the car or the motorcycle rider needs to be constantly alerted of the oil consumption patterns.

As a vehicle uses more engine oil, the pressure inflicted by the oil inside the engine drops. This hints at a loss of engine oil. There is a sensor connected to your engine to flash a red light whenever such a drop happens.

It is called the Oil Pressure Sensor. A pressure switch is used to activate the warning light. This light is set up in the dashboard of the car or the bike, and the flash is easily viewable to the driver. The oil pressure switch sets off whenever the pressure falls below a preset level.

The switch could be located inside the cylinder block itself. In some special case, the switch is in the oil filter housing or also on the engine head. This exact location of the oil pressure switch depends on the design of the engine specific to a car model.

A movable diaphragm or a self-elastic diaphragm, which contains hairspring, is the basic construction of the oil pressure sensor or switch. The spring design and construction establishes the critical pressure that is to be applied for the diaphragm movement. The usual operating range of engine oil pressure is between .25 and .75 bar, or 3.5 to 11 PSI.

The pressure may vary depending on the engine’s mandate. When the pressure dips below this range, the switch gets activated and an indication is seen at the car’s dashboard. A light glowing at the dashboard panel is the normal indication system.

The figure above is an illustrative representation of the Engine oil pressure switch:
Point 1 is the sealing washer, and it sits atop the thread for tightness, which is marked by 6.

As we move inside the sensor, we see the moving diaphragm at Point 2, and the switch housing at Point 3.

Point 4 is the connector and Point 5 is the switch contacts, which can be open or closed as per the pressure of the engine oil inside the system.

As can be seen, the basic principle is the same, wherein the switch contacts (Item no 5) can either open due to the movement of the diaphragm (Item 2) or in the other case, of a normally closed switch, the diaphragm movement would open the switch contact. Both cases trigger the circuit, which sends the signal to the dashboard indicator.

Probable Reasons for Engine Oil Pressure Fluctuation

There are three main reasons due to which we could notice engine oil pressure fluctuation. This, in turn, can lead to drop in the operating oil pressure.

The number one reason in this list is, “Low Engine Oil”. Checking of the engine oil level at regular interval is something of utmost importance. Under normal driving circumstances, the engine oil doesn’t burn out so fast. Its consumption rate is nothing compared to petrol consumption rates. So, there could be a tendency to overlook the engine oil levels on your dashboard.

Another common occurrence leading to swift engine oil pressure drops is a leak developing in the lines, which carry this oil from the oil reservoir to the engine cylinders. After it has reached the engine, there are different passages for the oil to exit the cylinder. There are numerous seals and washers in the line too.

A leak could be anywhere in this intricate setting. An authorized mechanic would be the best bet to check this part up.

Oil viscosity is another factor which could lead to oil pressure drop indication. This aspect can be best addressed by selecting quality engine oil. Both, lower or higher viscosity oils than that recommended by the particular engine manufacturer, are not advisable for use.

Low viscosity oil would not offer the correct lubrication effect to the piston and cylinder blocks, while higher viscosity oil would add its own frictional grind between the two moving parts.

Amongst the various properties of the engine oil, both physical and chemical, viscosity holds prime importance. Viscosity in layman terms refers to an object’s thickness.

When two metal surfaces move very close to each other, the oil in between the surfaces is unable to escape due to its viscosity. The oil itself is incompressible beyond the viscous limits. This helps in holding the two surfaces apart.

The oil pump is the main and also the only source that ensures flow of engine oil to all the required areas in the car. A faulty engine oil pump would, therefore, immediately lead to a drop in engine oil pressure. Once again, only a qualified mechanic can identify this defect and attend to it as necessary.

Symptoms of Engine Oil Pressure Sensor Malfunction

The engine oil pressure indicator, on the dashboard, remains continuously on or off or it blinks, depending on the state of its design.

There is, however, no way to ascertain the exact quantity of engine oil inside the vehicle. Whenever you notice the sensor flashing, contrary to how it usually does, it’s not too bold to assume that your sensor is raising a few red flags.

You can never be too sure what the real problem is, and so, it is best to not be a self-learned mechanic in such cases. The only way is seeking professional help at the earliest. In case such help is not immediately at hand, then the other symptoms as mentioned hereinafter are to be closely monitored for.

These symptoms, present or absent, would help the decision making process, if there is need for emergency action. Most cases, it would be an isolated occurrence and there would be ample time at hand to go to the closest servicing station for repair work.

Any change in the car’s performance accompanied by the sensor blinking madly would not be something you can ignore. In most cases, whenever there is a problem with the engine, the car’s ability to be driven is the first one to give in.

A drop in power while driving is one of the common symptoms reported by most people who have come across such an experience.

As mentioned earlier, the engine oil helps in lowering the heat amongst the moving parts inside the engine. An actual loss of engine oil in the system would lead to loss of driving power as well as increase in fuel consumption. These would be a sure-shot indication of a fault in the actual engine oil system.

There could also be an abnormal noise emanating from the engine whilst in running condition. In case of such an occurrence, the first step is to immediately switch off the engine. Any further running of the engine in this condition might just lead to extensive damage to the engine internals and can become explosive for the vehicle.

There is a chance that the engine light on the dashboard, which is a separate indicator, lights up due to low engine oil volume.

Finally, the worst case scenario is the engine seizing. This is a nightmare. So, to steer clear of this condition for as long as possible, all the other symptoms mentioned above need to be attended to at the first sign of occurrence.

Test for Engine Oil Pressure Sensor Serviceability

We have learnt there are two types of oil pressure sensors that are in use on different car engines. In the case of the switch, which has open contacts as default, we have to check for an open circuit condition when the engine is not running. In case of a closed contact switch, a short-circuit condition should exist.

A multi-meter would be needed to conduct this test. For a given engine in switched-off condition, we’ll first need to disconnect the connector from the pressure switch.

This would bring the two switch ends, the pins, into view. The multi-meter would indicate infinite resistance between the two pins in case of an open-contact pressure switch, and zero resistance in case of closed-contact pressure switch.

There are some engine oil pressure switches, which have only one pin. In that case, the resistance between that singular pin head and the engine body is to be checked.

A schematic diagram of the engine oil pressure switch and the multi-meter is depicted above. A multi-meter, therefore, would be a most-recommended item to be kept in your car’s toolbox always.

With the engine in running condition, just the opposite resistance reading should prove whether the switch is serviceable or indeed defective.

Running Vehicle with Defective Engine Oil Pressure Sensor

As mentioned, there is the probability that it’s the engine oil pressure sensor that’s acting nuts, while the rest of your system is still intact.

However, even if that is the case, you need to rush to your nearest auto expert!

With an aim to get to the closest servicing station in proximity, there is no reason to stop the drive. Before taking this decision, however, it is better to double check.

The dipstick provided under the car engine hood is the only tool required for this verification check. Dip the stick into the engine oil tank and draw it out. The oil stain on the dip stick would give some important clue on the health of the engine oil in real. It would give the level of engine oil in the tank. If there has been a real malfunction in the oil system, this level would be unduly low.

Checking the color of the oil on the dip stick would also give a good indication on the engine oil system as such. The color of good unadulterated engine oil is light amber and clear.

Running a finger over the dip stick would also provide tell-tale signs if any metal impurity has been drawn back by the system into the oil tank. Identifying any metal grains in the oil stain means that there has been an excessive friction between the engine cylinder heads. In this case, it is essential that the car is not driven any further. Help should be sought for, at the current site.

Time and Cost to Change Engine Oil Pressure Sensor

There is good news for all of us in this section. Any local mechanic has a stock of engine oil pressure sensors. If that is where the loophole is, don’t fret! Your vehicle can get a brand new oil pressure sensor in just a few seconds and the quality is reliable too.

Most authorized mechanics would charge approximately $50 to $70 for their services.

The replacement item too, the new pressure switch, is not so costly. It would be available for approximately $50 to $60. There would, however, be a marginal difference in these costs, depending on the type of car being serviced. The total cost of replacement of a defective engine oil pressure Sensor would therefore be about $130.

As the cost is not heavy on the pocket, it therefore goes without saying, that at the first signs of any malfunction in the engine oil pressure sensor, the closest and fastest service station to undertake its change is the most recommended way out.

A pressure switch in time would keep the engine rolling for a much much longer time.