The internal combustion engine needs oil just as much as it needs fuel, air, and coolant. For the oil to efficiently circulate from the sump through all the engine block channels and over moving parts within the engine, it must be pressurized.
An oil pump takes care of this pressurization. Since the oil pressure has to be within an optimal pressure to lubricate and cool every engine section, an oil pressure sensor monitors pressure levels. It reports this to the driver through a pressure gauge or an oil pressure warning light.
If the oil pressure sensor is bad, you will have no way of telling if your engine is running on the correct oil pressure. Luckily, there is a couple of symptoms that you could interpret as an anomaly in your sensor.
How Does an Oil Pressure Sensor Work?
An oil pressure sensor consists of a diaphragm and a spring-loaded switch. The diaphragm is exposed to the pressurized oil on one side and a contact pin assembly on the other side.
The contact pin assembly attached to the springs offers some resistance to the diaphragm’s movement.
As the oil pressure changes, the pressure applied to the diaphragm changes. This, in turn, moves the contact assembly a distance determined by the resistance of the spring.
If the pressure falls below a threshold, the springs push the contact assembly towards a contact point to finish a connection. This will trigger the low-pressure warning. When the pressure is too high, and the gauge can track this, a second conductor will engage when the oil pressure is above the threshold.
In cases where your oil pressure gauge shows gradual readings, the diaphragm connects to a resister that sends varied voltage to a processing unit depending on how hard the oil is pushing against the diaphragm.
The processing unit or oil pressure gauge translates this voltage to a reading displayed on your oil pressure gauge.
What Can Go Wrong on an Oil Pressure Sensor?
Oil pressure sensors rarely fail. This means false negatives are very rare. However, over time, something could go wrong. The possible fail points are:
In the Oil Pressure Sensor Itself
While an oil pressure sensor is rudimentary and rugged, the spring, diaphragm, or contactors aren’t invincible.
Over time, something might mechanically fail, affecting how the sensor interprets oil pressure. This could cause:
- A jam that keeps the sensor from detecting oil pressure as it builds up
- An erratic operation that keeps the sensor bouncing between low and normal oil pressure
- A damaged rheostat that doesn’t send varied voltage readings as oil pressure changes
- Dirt or debris blocking the oil pressure sensing surface
Since all these problems translate to odd readings on the oil pressure gauge that could also mean the oil pressure is low, you can’t narrow it down to the sensor without further troubleshooting.
Faulty Wiring
Your oil pressure sensor sends a voltage signal to the control module or oil pressure gauge via wiring. Depending on your gauge, it will have:
- A ground connection
- A signal wire
- A reference voltage wire
Any break in one of these contactors will read to erratic or false readings. Troubleshooting faulty wiring is the easiest way to troubleshoot problems with your oil pressure sensing system.
- Confirm that the connector harness is clean and firmly connected to the oil pressure sensor
- Inspect the wires running from the sensor to the module or gauge to confirm that they aren’t broken or chewed through
A Damaged Control Module or Gauge
While these are not directly part of the oil pressure sensor, they could affect its efficiency, especially if it’s a continuous reading system.
Just like your fuel level indicator, the oil pressure system consists of a sender unit (the sensor) and an interpretation or reporting unit. This could be a control module for a digital unit, a mere light for a single state system, or a preprogrammed analog display for a continuous display dial.
Symptoms of a Bad Oil Pressure Sensor or Switch
If there is a problem with the oil pressure sensor, they will translate to erratic or wrong readings on your oil pressure gauge or light. Here are some of the things to expect
A Blinking Oil Level Light
If the pressure sensor is faulty, it will give erratic on-off readings. This will make the oil warning light blink on and off on the dashboard.
Since this light also blinks when oil levels are low, you should use the dipstick (if your vehicle has it) to confirm that you have oil in the engine. Also, ensure that the oil is not old and change it if you are overdue for an oil change.
Wrong Readings on the Oil Pressure Gauge
Older vehicles had a mechanical gauge that translates readings from the sender unit to a needle position on the gauge.
If you have enough oil and the gauge still reads zero, it is either damaged or a faulty connection.
Luckily you can test it using a multimeter.
- Access the backside of the display
- Connect a multimeter to the ground, and the signal lead
- Turn on the car while monitoring the voltage readouts
- It should steadily sweep from the off voltage (reference) to a final voltage and almost steadily hold
- If this happens, then the display is the problem. If it doesn’t, there’s an issue with the sensor or the wiring to the sensor.
Modern vehicles are more complicated and use control modules and a CAN bus to report. A good OBDII scanner will detect anomalies in the system to access raw signals from the oil pressure sensor. You can use this to determine if the sensor is faulty or working fine and the problem is somewhere else in the system.
The Oil Pressure Light Turns On
The surest sign that you have an issue with something in your oil pressure system is the oil pressure light popping up.
This will only happen when you have lousy oil pressure, or your oil pressure sensor is defective and needs replacement. Don’t ignore this light. Troubleshoot the entire system to find out what is wrong.
Can I Keep Driving With the Oil Pressure Light On?
No. You should never keep on driving once the low oil pressure light comes on or your oil pressure gauge shows that you have low oil pressure. Assuming that the gauge is correct and not giving a false reading is better than ignoring it.
Some of the things that could be wrong when the warning comes up include:
You Are Low on Oil
If your oil levels dip too much, there won’t be enough to create sufficient oil pressure in the system. While this should be enough to trigger the low oil levels warning, it might not always do so.
Use the dipstick, digital or mechanical, to confirm your oil level readings. Apart from this, inspect the bottom of your vehicle and the engine bay to ensure that you don’t see any oil leaks.
We did a post on dropping oil levels. You can check it for ideas on where your oil might be going.
You Have Dirty Oil
If you bought a new car or haven’t changed the oil in a very long time, chances are it is dirty, and the levels have dipped.
Dirty oil clumps up and is harder to pump. This could jeopardize the system’s ability to bring it up to pressure. It could also block channels and prevent the sensor from detecting the correct pressure readings.
- Do an oil change if it is overdue.
- Inspect the quality of your current oil to ensure that it’s clean and with no contamination.
The Oil Pump Is Damaged
Another reason you might have low oil pressure is a damaged pressure pump. While this rarely happens, you should not dismiss the possibility.
If you have a damaged pump, Your engine won’t pull oil from the sump. Critical parts of the engine won’t be lubricated. It might even sound wrong, and you might get clunks and grinds.
This will damage the engine, hence why you shouldn’t keep driving once you get the low oil pressure warning. Find out why it’s popping up first.
The Oil Pressure Sensor or Sensing System is Faulty
A faulty oil pressure sensor is perhaps the most manageable problem to fix once your low oil pressure light pops up.
Getting a replacement is easy, and oil pressure sensors sit at an easily accessible spot on the engine block.
ProTip: After confirming that you have oil and your car isn’t due for an oil change, bench testing or replacing your oil pressure sensor with a good new one is a fast and straightforward way to troubleshoot the problem.