An oil pressure warning is one you should never ignore, even when the cause turns out to be a sensor. A P0520 code means the engine computer found a problem in the oil pressure sensor or switch circuit.
This guide explains how to check real oil pressure first, then how to test the sensor and its wiring step by step.
P0520 Code Breakdown
Every OBD-II code follows the same five-character pattern set by the SAE J2012 standard. Each character narrows down which system has the fault. This table shows what each part of the code tells you.
| Character | Meaning | What It Tells You |
|---|---|---|
| P | Powertrain | The fault is in the engine or transmission systems. |
| 0 | Generic (SAE) code | The definition is the same on every OBD-II vehicle. |
| 5 | Vehicle speed, idle control and auxiliary inputs | The fault involves vehicle speed, idle control or inputs such as oil pressure, A/C, power steering, system voltage and cruise control. |
| 20 | Specific fault | Engine Oil Pressure Sensor/Switch Circuit Malfunction |
What the P0520 Code Means
The SAE J2012 standard defines the P0520 code as Engine Oil Pressure Sensor/Switch Circuit Malfunction. The oil pressure sensor or switch screws into an oil passage on the engine block, oil filter housing or cylinder head. A switch simply opens or closes at a set pressure to turn the warning light on or off. A sensor sends a voltage that changes with pressure so the gauge and the powertrain control module (PCM) can read the actual value.
Most sensors get a 5-volt reference and a ground from the PCM and send back a signal between about 0.5 and 4.5 volts. Many warm engines make roughly 10 psi per 1,000 rpm, but the specification for your engine is what counts.
Some engines use the oil pressure reading to control variable valve timing or variable displacement oil pumps. That is why a bad reading can affect how the engine runs, not just the gauge.
This is the general circuit code for the oil pressure sensor or switch. The PCM saw a signal it could not accept, such as one that is missing, out of range or does not match a related input, but the code does not say whether the signal was too low or too high.
Symptoms of an Oil Pressure Sensor Fault
Always treat an oil pressure warning as real until you prove it is not. Common signs of a P0520 code include:
- Check engine light on
- Oil pressure warning light or message
- Oil pressure gauge reading zero, maximum or jumping
- Oil leaking from the sensor
- Valve timing codes on some engines
If the warning comes with ticking, knocking or low oil on the dipstick, stop the engine. Real low oil pressure can destroy an engine in minutes.
Common Causes of the P0520 Code
A general circuit fault can come from anywhere in the circuit. These are the usual causes:
- Loose or corroded connector. Moisture and heat attack the pins.
- Damaged wiring. Wires can chafe, break or melt near hot or moving parts.
- Failed oil pressure sensor or switch. Internal wear or damage stops it from reporting correctly.
- Problem with the 5-volt reference or ground. Shared circuits can affect several sensors at once.
- PCM fault. Rare.
Tools You Will Need
You can do most of this testing at home with basic tools:
- Mechanical oil pressure gauge kit
- OBD-II scan tool that shows oil pressure
- Digital multimeter with back-probe pins
- Oil pressure sensor socket
- Wiring diagram for your engine
How to Diagnose the P0520 Code
Check the oil level first, every time. Then test real oil pressure before you blame the sensor.
Check Live Data
With the key on and engine off, the oil pressure reading should be close to zero. With the engine running, it should rise and change with engine speed. A reading stuck near 0 or 5 volts confirms a circuit fault.
Inspect the Connector and Wiring
Find the oil pressure sensor or switch and check that the connector is fully seated and locked. Look for corrosion, bent pins and wiring that rubs on brackets or hot parts.
Test Reference, Ground and Signal
Back-probe the connector with the key on. The reference should read close to 5 volts, the ground close to 0 volts, and the signal should match the value your service manual lists. Any wire that fails tells you where to look next.
Check the Oil Level and Condition
Park on level ground and check the dipstick with the engine off. Top off if low. Look for sludge or metal particles, which point to engine wear that can lower real pressure.
Repairs That Clear the P0520 Code
Match the repair to what your tests found. Then clear the code and drive under the same conditions that set it.
- Top off or change the oil with the correct grade.
- Repair the connector or wiring.
- Replace the oil pressure sensor or switch if it fails tests.
- Fix a real low pressure problem such as a worn pump or clogged pickup.
- Replace a leaking sensor and clean oil from the connector.
Use thread sealant only if the service manual calls for it, and keep it off the sensor tip. Tighten the new sensor to the specified torque, since many have thin bodies that crack if overtightened.
Common Mistakes to Avoid
These mistakes waste money or leave the real fault in place:
- Replacing the sensor before checking the connector and wiring
- Ignoring other codes that share the same reference or ground
- Replacing the sensor without testing real oil pressure
- Driving on with a warning light and engine noise
Repair Cost Breakdown
The cost to fix a P0520 code depends on the cause. This table shows typical ranges for parts and labor.
| Repair | DIY Cost | Typical Shop Cost |
|---|---|---|
| Oil change | $30 to $80 | $50 to $120 |
| Oil pressure sensor or switch | $15 to $80 | $100 to $300 |
| Wiring or connector repair | $10 to $30 | $100 to $300 |
| Oil pressure test | $0 with a borrowed gauge | $50 to $150 |
The sensor is usually cheap, though some are hard to reach behind the intake or under the oil filter housing. Real low oil pressure repairs, such as an oil pump, cost far more.
Is It Safe to Drive with a P0520 Code?
Only after you check the oil level and are sure the engine has real oil pressure. If the oil level is low, the engine makes noise or you are not sure, do not drive it.
If a mechanical gauge shows good pressure, the engine is safe to drive while you fix the sensor, but you lose your early warning for real oil loss.
Related Codes
These codes often show up with this one or point to the same system:
| Code | Meaning |
|---|---|
| P0521 | Engine Oil Pressure Sensor/Switch Circuit Range/Performance |
| P0522 | Engine Oil Pressure Sensor/Switch Circuit Low Voltage |
| P0523 | Engine Oil Pressure Sensor/Switch Circuit High Voltage |
| P0524 | Engine Oil Pressure Too Low |
| P0011 | A Camshaft Position Timing Over-Advanced or System Performance (Bank 1) |
Fixing the Oil Pressure Sensor Circuit
A P0520 code means the PCM found a fault in the oil pressure sensor or switch circuit. Leaking sensors, corroded connectors and damaged wiring cause most cases.
- Check the oil level first.
- Test real oil pressure with a mechanical gauge.
- Inspect the connector and wiring.
- Replace the sensor only after the tests point to it.
Frequently Asked Questions
Is the P0520 Code the Same as Low Oil Pressure?
No. It means the PCM found a problem with the sensor circuit. P0524 is the code for real low oil pressure. Still, check the oil level and test real pressure, since a failing engine can look like a sensor fault.
Where Is the Oil Pressure Sensor?
It screws into an oil passage, often near the oil filter, on the engine block or under the intake manifold. On some V8 engines, it sits at the back of the engine under the intake. Your service manual shows the exact location.
What Is Normal Oil Pressure?
It varies by engine. A common rule is about 10 psi per 1,000 rpm on a warm engine, with at least 5 to 10 psi at hot idle. Check the specification for your engine.
Can a Leaking Sensor Cause This Code?
Yes. Oil can leak past a failing sensor into its connector, which causes signal errors. Replace the sensor and clean the connector with electrical contact cleaner.
Should I Use an Original Sensor?
It is often a good idea. Some low-cost sensors read slightly off, which can set a range code or make the gauge read wrong. Match the part number for your engine.