An oil pressure sending unit controls either the oil pressure light or gauge on your dashboard. When the oil pressure sender unit detects oil pressure in the vehicle, a switch trips, and then two things could happen: either the light will shut off, or the gauge will become active.
Basically, the oil pressure sending unit is what sends the oil pressure information to the car’s computer, which then controls the related lights and gauges in your dashboard.
A faulty oil pressure sending unit can result in inaccurate oil pressure readings and warnings. So, it is important to recognize the signs of a sending unit that needs to be replaced.
Some of these repairs are easy tasks for a seasoned DIYer and will not require a costly visit to a mechanic or auto dealer shop.
What is an Oil Pressure Sending Unit?
A vehicle’s oil pressure sending unit is a mechanical device that controls oil flow in the engine compartment. This is crucial for sending information about the vehicle’s oil pressure to the computerized system, which will operate the related indicators.
Both the oil pressure indicator gauge and the oil pressure warning light indicator rely on the information received from the vehicle’s computerized system to operate properly.
The computerized system, in turn, depends on the oil pressure sending unit to send the signals needed to communicate with the gauge and dashboard warning light.
So, if the oil sending unit malfunctions, then a wrong signal or even no signal will be transferred to the computerized system.
Based on that input from the oil sending unit, the computerized system will send a signal to the gauge and the dashboard oil pressure warning light accordingly.
Ok, now, have you been confused by somebody referring to a vehicle’s oil sending unit with the names “oil pressure switch” or “oil pressure sensor”? Let’s explore if these are actually different or if any of them are the same.
Oil Pressure Switch
An oil pressure switch is a small but key device in your vehicle’s engine, usually located on the engine block or near the oil pump. Its job is to monitor the oil pressure inside the engine’s lubrication system.
The switch usually works as a simple on/off sensor, closing or opening an electrical circuit based on oil pressure. This makes it a reliable way to monitor your engine’s health.
Oil Pressure Sensor
If you’re asking, “How does an oil pressure sensor work?” the oil pressure sensor of a vehicle is a mechanical device that will read the pressure of the oil in the engine and send a signal to the computerized system of the vehicle that transmits the readings to the vehicle’s oil pressure gauge and warning light.
An oil pressure sensor is technically used to refer to both the oil pressure sender and the oil pressure switch. Therefore, you could say they have similar functions. But there is a slight difference. So, stay tuned for the next section below.
Oil Pressure Switch Vs. Sensor Differences
When you think about the oil pressure sending unit vs. the oil pressure sensor, they may seem like they do the same job, so you can think of them as interchangeable. However, the minor difference between the two is:
- The oil pressure switch merely illuminates the oil pressure warning light when it detects low oil pressure.
- An oil pressure sensor reads the oil pressure and sends the oil pressure information to the oil pressure gauge for readout.
How does the Oil Pressure Sending Unit function?
The functionality of an oil sending unit depends on whether it is designed to feed a dashboard gauge or simply trigger a warning light. For vehicles equipped with a gauge that displays a numerical pressure reading, the sending unit is a variable resistor, also known as a transducer.
Inside this unit, pressurized engine oil pushes against a flexible diaphragm, which moves a contact across a resistive winding. This physical movement changes the electrical resistance of the circuit proportional to the oil pressure, creating a continuous and analog signal.
The variable resistance signal is interpreted by the dashboard gauge or the engine control unit (ECU). For instance, a low-pressure condition will correspond to a high resistance value, while a higher pressure will result in a lower resistance value.
In contrast, an oil pressure switch, used for a simple dashboard warning light, operates on a binary on/off principle. This switch contains a set of electrical contacts that are held open by oil pressure when it is above a predetermined safety threshold, often between 3 and 10 pounds per square inch (PSI).
If the oil pressure drops below the factory-set minimum, the pressure on the diaphragm releases, allowing a spring to close the internal contacts. This action completes the electrical circuit, which immediately illuminates the red oil pressure warning lamp on the dashboard.
Modern vehicles may use a sensor to transmit the full pressure range to the ECU, which then processes the data to control a dashboard gauge and still activate a warning light if the pressure falls into a dangerous range.
Symptoms of a Bad Oil Pressure Sending Unit
A vehicle’s oil pressure sending unit is part of the essential components that shouldn’t be overlooked when it malfunctions. The part is designed in a manner that is easy to detect when it fails or goes bad. Some of the bad oil pressure sending unit symptoms include;
#1. Oil pressure warning light display.
One of the first symptoms of a bad oil pressure sending unit is that the oil pressure warning light comes on automatically. As soon as the oil sending unit fails, it turns on the warning light and keeps it on until the oil sending unit is fixed.
Sometimes you will check the oil level to find out that everything is actually okay. In that case, you can take it as a quick notification that the oil sending unit is progressively getting worse and needs immediate attention.
#2. Inconsistent (blinking) display of oil pressure warning light.
Another symptom very similar to what we stated above is the inconsistent display of blinking of the oil pressure dashboard warning light. While the lights stay on in the first instance, they turn on and off immediately in this case.
When the oil pressure light constantly goes on and off, it’s a solid indication that there is a problem forthcoming with the oil pressure sending unit, and it would be beneficial to have it checked out to prevent further damage.
#3. Inaccurate oil pressure gauge readings.
Is the oil pressure gauge of your vehicle showing zero from morning until evening, and the following day? That’s it! There is a problem with the car’s oil pressure sending unit. Sometimes, the gauge may read less or more than the car’s actual oil pressure.
The symptoms described above are also generally the same as oil pressure switch symptoms. In any case, if you see any of the three symptoms above, it’s not the time to ignore and just manage your car driving around.
It is not even the right time to procrastinate after seeing these symptoms. You should always check the oil level immediately if you have seen these symptoms, and if you are unable to resolve the issue yourself, then it is time to call a specialist auto mechanic.
How Do You Test An Oil Pressure Sending Unit?
If you discover that your vehicle’s oil pressure sending unit is failing, it is the right time to test the component to figure out whether it is something to worry about or not. Here is a straightforward step-by-step guide on how to test an oil pressure sensor or sending unit.
Step 1: Put the key into the ignition and turn it to the accessory position
Put the key in your vehicle and turn it to the accessory position, so you can begin the oil pressure sending unit test.
Step 2: Look at the dashboard oil pressure gauge
Now that you have turned the key to the accessory position, look at the dashboard oil pressure gauge. If it reads zero on the dashboard, disconnect the wire on the oil sending unit. If it reads up to 3, then the oil sending unit is bad and needs to be replaced.
Step 3: Test the disconnected wire on a metal part
You can also take the wire you just disconnected from the oil sending unit and touch it to the vehicle’s battery negative terminal or any metal part of the vehicle. Check again; if the oil pressure gauge appears zero (0) on the dashboard, it means the oil sending unit is good.
How To Replace Bad Oil Pressure Sending Units?
Most types of oil pressure sending units light up when the oil pressure has reached nine pounds or less. However, there are times when the unit malfunctions so that even if the pressure has reached below the critical level, the warning lights do not light up, such as when the issues mentioned above are present.
When this happens, you need to replace the oil pressure sending unit immediately to avoid serious problems with your car. Remember that when your car runs out of oil pressure, its engine can sustain serious damage.
Step 1 – Locate the Oil Pressure Sending Unit.
Before you start working on the oil pressure sending unit in your car, make sure your vehicle is in a safe and secure position. To do this, pop the hood of the car, then prop the front of the vehicle using car jack stands.
After putting your car in a secure position, locate the oil pressure sending unit. You should be able to find the unit very close to the oil filter. The pressure unit on newer car models usually has a round black ½ inch long cylinder, with two wire connectors. Older car models usually have small round units that are 1½ inches wide.
Step 2 – Check the Oil Pressure Sending Unit.
To make sure that the problem is in the oil pressure sending unit, check the electrical connection of your car and make sure that the oil pressure sending unit is properly connected. If the electrical connections of your car are good, but the oil pressure sending unit still fails, then it is time to change the unit.
Step 3 – Remove the Old Oil Pressure Sending Unit.
To remove the old oil pressure sending unit, squeeze the connector, then pull it off using your gloved hand. After removing the connector, unscrew the unit and then lift it out.
Install the new unit inside the place where you remove the old one. Wrap Teflon tape around the threads of the new unit and then thread it into place.
Make sure that it’s not too tight, or the threads may break.
Step 4 – Reinstall the Electrical Connector.
After installing the new unit, attach the electrical connector to the unit. Turn on the power of your car and see if the oil gauge works. If the oil gauge does not work, check the electrical connection and make sure that it is installed properly.
Once you’re sure that the new oil pressure sending unit is properly connected to your car, close the hood of the vehicle and remove the car jacks.
FAQs.
Q: Can I still drive with a bad oil pressure sending unit?
Yes, you can drive with an inferior oil pressure sensor or sending unit because it doesn’t actually affect the smooth performance of driving your vehicle. Its job is to relay your vehicles oil pressure to the computer system of your vehicle at all times.
Driving with a defective sending unit is not recommended because although the function is simple, neglecting it for a long time can create some serious long-term problems for you.
How can you determine an oil pressure lower than ideal if your vehicles oil pressure sending unit is I defective?
If you decide to drive with a bad oil pressure sending unit you will certainly risk serious damage. Since it’s not that costly of a repair item, why delay and risk more serious damage?
Q: What happens when an oil sending unit fails?
When there is a failure of the oil sending unit of the vehicle, it will automatically display incorrect reading on the gauge.
Thus, this is false information, which means the opportunity for the driver to detect a problem with the vehicles oil flow process is non-existent.
Once the oil sending unit fails to display an incorrect reading for long enough, the oil pressure warning light will then be displayed.
You can easily resolve that problem by replacing the oil sending unit as soon as you notice it. It will probably not cost you very much.
Q: What is the cost to replace an oil sending unit?
To replace an oil pressure sending unit, won’t take you a full year’s savings. The cost for the part is $48 to $67, and the labor cost is $73 to $93.
So why wait one more day when you can just spend a few bucks for an oil sending unit replacement from $121 to $160? Still, the cost will differ from place to place.
The invoice amount for an oil sending unit is a sum of the parts dealer price and the labor cost by an auto mechanic for that part replacement and may involve other costs in addition to the $121 to $160 cost of a part and labor by a mechanic.
In any case, it’s worth it so stop thinking and just get it done.
Q: Is the oil pressure switch and sensor the same?
Let me say that the oil pressure switch and sensor are not the same when you are talking about an oil pressure switch vs sensor because they have different functions.
The oil pressure switch is the device that is a protective mechanical device that alerts on the condition that the oil in the car is not being adequately delivered, generally called low oil pressure.
When pressure is lost, it will indicate to the driver in the dashboard by triggering the oil pressure warning light display.
While it does monitor oil delivery, its relay only functions to on or off the light that the indicator uses to warn you about oil pressure.
The oil pressure sensor is used to measure the oil pressure of the vehicle. It will send a signal to send the reading to the gauge on the dashboard to warn the driver there is a potential problem that will happen in the engine compartment.
Q: How long does it take to replace the oil pressure Sending Unit?
The time it will take to replace an oil pressure sending unit for a vehicle will take less than a day. The job could take 45 minutes to a couple of hours, depending of course on the person replacing the oil sending unit.
If you have been working on your own vehicle as a DIYer for many years, you won’t spend as much time as the person who is doing their first minor repair on their own vehicle.
The process will also be a lot quicker for a professional auto mechanic because they typically do repairs on vehicles like that every day.
If you decided to go with an expert auto mechanic to replace the oil sending unit on a vehicle, you will probably be ready to drive your car within the same day compared to doing it yourself.
Regardless of which option you choose, pick the option that is better for you.
Q: Do I need to drain oil to change the oil pressure switch?
You don’t have to drain the motor oil from the vehicle when you change the oil pressure switch. This is nothing to worry about. An oil pressure switch can be changed in a few steps:
- Shut off the vehicle engine, and let it cool.
- Open the hood and disconnect the battery cables from the terminals.
- Locate the oil pressure switch on the engine block.
- Disconnect the wire on the oil pressure switch.
- Take the oil pressure switch off with its removal socket.
- Put sealant on the new oil pressure switch.
- Put the switch in the engine block by hand and tighten it with the same socket.
- Reconnect the wire to the switch and start the vehicle to finalize it.
Final Words
It’s easy to get the terms “oil pressure sending unit,” “oil pressure switch,” and “oil pressure sensor” confused. This article has revealed the small difference in their function.
Now that we have defined what a sending unit is, if you have a bad oil sending unit, it may not keep your engine from running, but it will have some symptoms.
You should pay attention to any symptoms and do the necessary repairs, so you don’t cause further damage.