# P0520: Engine Oil Pressure Sensor/Switch "A" Circuit **Verdict:** Drive to a shop this week Engine sensors - Generic OBD-II code, applies to all gasoline cars and light trucks sold in the US since 1996. - **Typical cost:** $100-$450 - **Urgency:** This week - **Most likely:** Failed oil pressure sensor or wiring - **DIY?:** Check oil first; often DIY ## Quick answer P0520 means the engine computer has found a fault in the oil pressure sensor or switch circuit, so it cannot trust its oil pressure reading. Most often the sensor or its wiring has failed. But if the oil pressure light is on, the gauge reads low, or the engine is ticking or knocking, stop the engine right away, because the oil pressure may really be low. ## What does P0520 mean? Every engine needs oil under pressure to keep a thin film between its bearings, camshafts, and other moving parts. The oil pump creates that pressure, and an oil pressure sensor or switch, usually screwed into the engine block, oil filter housing, or cylinder head, reports it. A switch simply turns the warning light on when pressure falls very low. A sensor sends a voltage that rises with pressure, so the computer can drive a gauge and, on many engines, manage variable valve timing or a variable oil pump. P0520 is the general circuit code for oil pressure sensor or switch "A." The computer sets it when the signal is missing, erratic, or wrong in a way that does not fit a more specific fault, and on many vehicles it can set within one trip. Some makers use P0520 where others would set P0521, P0522, or P0523. A circuit code does not prove the oil pressure is fine, so a mechanical gauge test is the safe way to know. ## What are the symptoms of P0520? - Check engine light on, sometimes with the oil pressure warning light - Oil pressure gauge reading zero, maximum, or jumping around - Low oil pressure message even though the oil level is correct - Oil seeping from the sensor or into its electrical connector - Ticking or knocking from the engine only if oil pressure is truly low ## What causes P0520? Ranked from most to least likely. Check them in this order: the cheap, common causes first. 1. **Failed oil pressure sensor or switch** (most common). The sensor sits in hot, pressurized oil and goes through constant heat cycles. Its internal diaphragm or electronics can fail and send no signal or a wrong one, and many leak oil at the body or into the connector. Oil inside the connector, or a gauge that dropped to zero while the engine sounds normal, points here. 2. **Damaged wiring or connector** (common). The sensor connector often sits low on the engine or near the exhaust, where heat, oil leaks, and vibration crack it. A broken locking tab can let it work loose. A wire rubbed through near the block or a corroded pin can cut the signal entirely or make the reading drop out intermittently over bumps. 3. **Low oil level or genuinely low oil pressure** (less common). Low oil, a clogged filter, worn engine bearings, or a failing oil pump can make a working sensor report readings the computer flags. That is why the oil level must be checked and, if there is any doubt, pressure confirmed with a mechanical gauge before the sensor is replaced. Never assume a sensor fault if the engine is noisy. 4. **Wrong replacement sensor** (rare). Oil pressure sensors and switches can look alike but differ in pressure range, thread, and electrical design. Installing a switch where a sensor belongs, or a part with the wrong range, can set circuit codes and give false readings. When P0520 appears right after a sensor replacement, check the part number against the engine. ## How do you diagnose P0520? 1. Check the oil level and condition on level ground with the engine off, and top up if it is low. 2. If the oil light is on or the engine is noisy, do not keep running it; have the pressure checked first. 3. Have a shop fit a mechanical oil pressure gauge in place of the sensor to read the real pressure. 4. Inspect the sensor connector and wiring for oil, corrosion, and damage, and check the reference voltage and ground. 5. Compare the scan tool reading with the mechanical gauge at idle and at higher engine speed. ## How do you fix P0520, and what does it cost? | Fix | Typical cost | What it involves | | --- | --- | --- | | Mechanical oil pressure test | $100-$200 | Confirms whether the engine actually has good pressure. | | Replace oil pressure sensor or switch | $100-$400 | Higher on engines where the sensor sits under the intake or at the back of the engine. | | Repair wiring or connector | $100-$400 | Includes cleaning oil out of the connector. | Full price breakdowns: [oil change cost](/cost/oil-change), [engine replacement cost](/cost/engine-replacement). ## Is it safe to drive with P0520? > **Drive to a shop this week.** Only if the oil level is correct, the engine sounds normal, and a test confirms pressure is good. If the oil pressure light is on, the gauge reads low, or the engine ticks or knocks, stop the engine as soon as it is safe and do not restart it, because running without oil pressure can destroy an engine quickly. ## Will P0520 fail an emissions test? In most states, P0520 with the check engine light on fails an OBD-based emissions test, even though oil pressure is not part of the emissions system. Clearing the code after the repair resets every readiness monitor, so drive several days of mixed trips before testing to let the monitors finish. ## After the repair: clearing P0520 After the repair, clear the code and start the engine. The oil light should go out within a few seconds, and the gauge, if your car has one, should rise to a normal reading and change with engine speed. Drive normally and recheck for a pending code after several trips. A returning P0520 means the wiring needs closer testing. ## How to prevent P0520 - Check the oil level every few fuel fill-ups and before long trips. - Change oil and filter on schedule with the viscosity listed in the owner's manual. - Fix oil leaks near the sensor so oil does not soak its connector and wiring. - Use the correct sensor part number for your engine when replacing it. - Never ignore a flickering oil light at idle; have the pressure checked promptly. ## Codes often seen with P0520 - [P0521](/codes/p0521): Engine Oil Pressure Sensor/Switch "A" Circuit Range/Performance - [P0522](/codes/p0522): Engine Oil Pressure Sensor/Switch "A" Circuit Low - [P0523](/codes/p0523): Engine Oil Pressure Sensor/Switch "A" Circuit High - [P0524](/codes/p0524): Engine Oil Pressure Too Low - [P0011](/codes/p0011): "A" Camshaft Position - Timing Over-Advanced or System Performance (Bank 1) ## Frequently asked questions ### Can I drive with a P0520 code? Only if you are sure the oil pressure is actually fine. If the oil light is on, the gauge reads low, or the engine makes ticking or knocking noises, stop the engine and have the car towed. If the oil is full and the engine sounds normal, drive gently to a shop soon. ### Does P0520 mean my engine has low oil pressure? Not necessarily. P0520 means the computer found a problem in the sensor or its circuit, and the most common cause is a failed sensor or wiring. Still, low oil can cause similar readings, so check the oil level first and have the pressure confirmed with a mechanical gauge. ### How much does it cost to fix P0520? Most P0520 repairs cost $100 to $450 at an independent shop. A mechanical oil pressure test runs about $100 to $200, a new sensor $100 to $400 depending on access, and a wiring repair $100 to $400. Genuine engine oil pressure problems cost far more to repair. ### What is the difference between an oil pressure sensor and a switch? A switch only turns the oil light on or off at a set low pressure. A sensor sends a changing signal so the computer can show a gauge reading and, on many engines, control valve timing or a variable oil pump. Some engines have both a sensor and a switch. ### Can low oil cause P0520? It can. If the oil level is low enough that pressure drops or fluctuates, the reading may fall outside what the computer expects. Check the dipstick with the engine off on level ground. If it is low, top up with the correct oil, and find out why it was low. ### Can I replace an oil pressure sensor myself? Often yes, if it is easy to reach. Most screw into the block or filter housing and need a deep socket or a special sensor socket. Expect a little oil to drain out, use thread sealant only if specified, and check for leaks afterward. Some sensors sit under the intake, which is harder. ### Why is my oil pressure gauge reading zero with P0520? A gauge stuck at zero with P0520 often means the sensor or its wiring has failed, especially if the engine sounds normal and the oil is full. But you cannot be sure without testing. Treat it as real low pressure until a mechanical gauge proves otherwise, and avoid driving any distance. ### Will P0520 make me fail an emissions test? Yes, in most states any stored code with the check engine light on fails an OBD-based test, including P0520. After the repair, clearing the code resets the readiness monitors, so drive several days of mixed trips before your inspection to let them finish. ### What happens if I ignore P0520? If the sensor is simply faulty, you lose your early warning of a real oil problem, which is risky. If the oil pressure is genuinely low, continuing to drive can wear out the bearings and destroy the engine. Either way, get it diagnosed rather than living with the light. ### Can P0520 affect variable valve timing? Yes, on some engines. The computer uses oil pressure readings to manage variable valve timing or a variable oil pump, and it may limit those systems if it cannot trust the sensor. Timing codes such as P0011 can also appear when real oil pressure or oil condition is poor. ## Sources - [SAE J2012: Diagnostic Trouble Code Definitions](https://www.sae.org/standards/content/j2012_201812/) - [EPA: On-Board Diagnostics (OBD)](https://www.epa.gov/state-and-local-transportation/vehicle-emissions-board-diagnostics-obd) ## Other engine sensors codes - [P0500 Vehicle Speed Sensor "A"](https://diagxcar.com/codes/p0500) - [P0505 Idle Air Control System](https://diagxcar.com/codes/p0505) - [P0506 Idle Air Control System RPM Lower Than Expected](https://diagxcar.com/codes/p0506) - [P0507 Idle Air Control System RPM Higher Than Expected](https://diagxcar.com/codes/p0507) - [P0521 Engine Oil Pressure Sensor/Switch "A" Circuit Range/Performance](https://diagxcar.com/codes/p0521) - [P0522 Engine Oil Pressure Sensor/Switch "A" Circuit Low](https://diagxcar.com/codes/p0522) - [P0523 Engine Oil Pressure Sensor/Switch "A" Circuit High](https://diagxcar.com/codes/p0523) - [P0524 Engine Oil Pressure Too Low](https://diagxcar.com/codes/p0524) - [P0562 System Voltage Low](https://diagxcar.com/codes/p0562) - [P0571 Brake Switch "A" Circuit](https://diagxcar.com/codes/p0571) ## Symptoms - [Why is my engine knocking?](https://diagxcar.com/symptoms/engine-knocking-noise) - [Why is my car leaking oil?](https://diagxcar.com/symptoms/car-leaking-oil) ## Repair costs - [Oil change cost](https://diagxcar.com/cost/oil-change): $45-$150 - [Engine replacement cost](https://diagxcar.com/cost/engine-replacement): $4,000-$12,000 --- Source page: https://diagxcar.com/codes/p0520 Updated: 2026-11-03 General information, not a substitute for a qualified mechanic.