P0520 means the engine computer has found an electrical fault in the engine oil pressure sensor or switch circuit. The sensor, its wiring or its connector is not behaving like an intact circuit. It is not, by itself, a report that oil pressure is low. But it does mean the one device that watches your oil pressure can no longer be trusted, in either direction. The warning light and gauge may complain when pressure is fine, or stay quiet when it is not. So the first job with P0520 is to confirm real oil pressure with a mechanical gauge, and only then repair the circuit. This article covers what sets P0520, the six real causes in order of likelihood, how to check actual oil pressure, and what each repair typically costs.
Start with the table, then read the triage note under it.
| Cause | Telltale Sign | Typical Cost |
|---|---|---|
| Failed oil pressure sensor or switch | Mechanical gauge shows good pressure; sensor output wrong or erratic | $50 to $300 installed |
| Oil-soaked, corroded or loose connector | Oil inside the connector; code comes and goes | $20 to $200 |
| Damaged wiring or a shared reference or ground fault | Chafed or heat-damaged harness; other sensor codes at the same time | $50 to $300 |
| Known sensor defect covered by a bulletin | Your vehicle is listed in a manufacturer bulletin for P0520 | $0 to $300 |
| Wrong or miswired replacement part | Code or odd readings started after the sensor was replaced | $0 to $200 |
| Genuinely abnormal oil pressure | Mechanical gauge reads low; engine ticking or knocking | $0 to $4,000+ |
Stop the engine immediately if the red oil pressure warning is on, the engine is ticking, tapping or knocking, or the oil level is low. Do not assume a P0520 means the warning is false. Low oil pressure can destroy an engine within minutes. Check the oil level first. If it is correct, the engine is quiet and the warning light is off, the car can be driven gently a short distance to have the pressure checked with a mechanical gauge.
What P0520 Actually Means
Most engines have either an oil pressure switch, which simply opens or closes at a set pressure to turn the warning light on and off, or an oil pressure sensor, which reports actual pressure as a varying voltage so the engine computer can drive a gauge and, on some engines, control a variable oil pump or other systems. On many modern vehicles the sensor feeds the engine computer, which then decides what the dashboard shows.
P0520 is “engine oil pressure sensor/switch A circuit”. It is the general electrical code for that circuit, set when the signal or circuit voltage is outside what an intact sensor and wiring can produce. Its neighbours are more specific: P0522 and P0523 for circuit low and high voltage, P0524 for oil pressure actually too low, and P0521 for a signal that is electrically plausible but does not make sense for the engine’s conditions.
Why You Must Check Real Oil Pressure First
This is the point that protects the engine. P0520 says the circuit is faulty, which is usually a cheap repair. But a faulty circuit also means the dashboard cannot be relied on to warn you if pressure really does drop. That is not a theoretical risk. Isuzu’s recall 22V-434 covered 2022 NQR and NRR trucks with the 6.0L gasoline engine whose harness was wired incorrectly at the oil pressure sensor connector. As a result, the engine computer “(and a technician’s scan tool) will not detect the condition for low oil pressure and will always perceive the pressure to be at 126 PSI”, so the warning light would never come on. That is a miswiring rather than a P0520 case, but it shows the danger. When the oil pressure circuit is wrong, both the dashboard and a scan tool can confidently report the wrong number.
The only independent check is a mechanical oil pressure gauge. It screws into the sensor port, or a tee fitting, and reads pressure directly, with no electronics involved. Compare its reading at idle and at around 2,000 to 3,000 rpm, hot, with the specification for your engine. If the mechanical gauge reads normal, the engine is healthy and P0520 is an electrical repair. If it reads low, you have a real oil pressure problem that needs attention before anything else. The site’s guide to how long an engine can run with low oil pressure explains why that matters.
Do not treat a normal-looking dashboard gauge as a substitute. On many vehicles the oil pressure gauge is buffered by the instrument cluster or engine computer, so the needle sits in the middle of its range across a wide band of real pressures and only moves when the reading passes a threshold. That makes it a warning device rather than a measuring instrument. A needle in the middle, or an oil light that stays off, tells you less than it seems, especially when the circuit behind it has just set a fault code.
Symptoms You May Notice Alongside the Code
The most common is an oil pressure warning light or gauge that behaves in ways a real oil system cannot. It flickers at steady speed, reads zero with the engine running quietly, or sits at maximum all the time. Sometimes the only sign is the check engine light. The site’s articles on the symptoms of a bad oil pressure sensor and an oil light that is on while the oil is full cover these patterns. What P0520 should not come with is engine noise. Ticking, tapping or knocking alongside a low reading means the pressure may genuinely be low.
1. Failed Oil Pressure Sensor or Switch
The sensor lives in a hot, vibrating spot, usually screwed into the block, cylinder head or oil filter housing, and its diaphragm and electronics eventually fail. Once the mechanical gauge has confirmed good pressure, check the sensor’s output. On a three-wire sensor, check for its 5-volt reference and ground at the connector, then compare the signal voltage with the pressure on the mechanical gauge. On a two-wire or single-wire switch, check that it opens and closes as specified. A sensor whose output does not track real pressure is faulty.
2. Oil-Soaked, Corroded or Loose Connector
An oil pressure sensor that starts leaking internally can push oil past its own body into the electrical connector, and in bad cases oil wicks along the wires inside the insulation. Oil in a connector interferes with the signal, and the fault will return even with a new sensor if the contaminated connector is left in place. External oil leaks from nearby gaskets can soak the connector from outside. Unplug it and look inside. Oil, corrosion, a broken locking tab or spread terminals are all common findings. Clean or replace the connector, and trace the wiring back to see how far any oil has travelled.
3. Damaged Wiring or a Shared Reference or Ground Fault
The sensor’s wiring runs near hot engine parts and can chafe or melt. On many engines the oil pressure sensor also shares its 5-volt reference and sensor ground with other sensors. A short in another sensor on the same reference circuit, or a poor shared ground, can pull the oil pressure signal out of range, and the giveaway is several sensor codes setting at once. With a wiring diagram, check each wire for continuity end to end, and check the reference voltage with the other sensors on that circuit unplugged one at a time.
4. Known Sensor Defect Covered by a Bulletin
Some vehicles have a documented P0520 problem. Chrysler Group’s service bulletin 18-034-14 Rev. A, titled “P0520 – Engine Oil Pressure Sensor Circuit”, covered a long list of 2013 and 2014 models built on or before March 12, 2014. The list included the Dart, Charger, 300, Challenger, Grand Caravan, Grand Cherokee, Cherokee, Durango, Journey, Wrangler, Ram trucks and the ProMaster, with the 2.0L, 2.4L, 3.0L, 3.2L, 3.6L, 5.7L, 6.4L and 8.4L engines. The repair was replacing the oil pressure sensor with a revised part, with different part numbers for different engines. It is always worth checking for bulletins before diagnosing further.
5. Wrong or Miswired Replacement Part
Oil pressure sensors and switches that share a thread and even a connector shape can have completely different outputs. Fitting a switch where the computer expects a variable sensor, or a sensor with a different pressure range, produces a circuit fault or nonsensical readings straight away. As the Isuzu recall shows, wiring errors can also produce a reading that looks plausible but is completely wrong. If P0520 or strange readings started after the sensor was replaced, check the part number and the connector wiring against the service information.
6. Genuinely Abnormal Oil Pressure
P0520 is an electrical code, but it can appear on an engine that also has a real oil pressure problem, and a sensor pinned at an extreme reading can look like a circuit fault. That is why the mechanical gauge check comes first. If it shows low pressure, the causes are mechanical: low or diluted oil, the wrong viscosity, a clogged pickup screen, a worn oil pump or worn engine bearings. The site’s article on whether a coolant leak can cause low oil pressure covers one of the less obvious causes.
Diagnostic Order
- Check the oil level and condition, and listen for ticking or knocking.
- Test real oil pressure with a mechanical gauge, hot, at idle and higher rpm, against specification.
- If pressure is low, stop and diagnose the oil system. The code is the lesser problem.
- If pressure is good, check for service bulletins.
- Inspect the connector for oil, corrosion and damaged terminals.
- Check the reference, ground and signal with a wiring diagram, and look for other sensor codes on the same reference circuit.
- Replace the sensor with the correct part only once the tests point at it.
Repair Cost
Typical costs, labelled as typical because sensor location varies between engines:
- Mechanical oil pressure test: roughly $50 to $150 at a shop. The most valuable money spent on this code.
- Oil pressure sensor or switch: roughly $50 to $300 installed. Sensors under intake manifolds or behind other parts cost more in labour.
- Connector or pigtail replacement: roughly $20 to $200.
- Wiring or reference circuit repair: roughly $50 to $300.
- Real oil pressure repairs: from an oil change to several thousand dollars for an oil pump or bearing work.
Can You Keep Driving With a P0520 Code?
Only once you know the real oil pressure is good. If the oil level is correct, the engine is quiet and a mechanical gauge confirms normal pressure, P0520 is an electrical fault and the car can be driven while you arrange the repair. Remember, though, that the dashboard may not warn you if pressure drops, so check the oil level regularly until it is fixed.
If you cannot check the pressure, treat any red oil warning as real, stop the engine, and have the car transported rather than risk it.
Related Codes
- P0521: oil pressure sensor range or performance. The signal is electrically plausible but does not match what the engine is doing, which can be the sensor or real pressure. See the P0521 guide.
- P0522 and P0523: oil pressure sensor circuit low and high voltage. More specific versions of the electrical fault P0520 describes.
- P0524: engine oil pressure too low. Unlike P0520, this says the pressure itself is low. Treat it as urgent.
- P06DD and P06DE: oil pressure control circuit faults on engines with a variable-displacement oil pump, which use the oil pressure sensor’s reading to control the pump.
Frequently Asked Questions
What does the P0520 code mean?
P0520 means the engine computer has found an electrical fault in the oil pressure sensor or switch circuit. It is not by itself a report of low oil pressure, but it means the sensor that watches oil pressure cannot be trusted until the circuit is repaired.
Is it safe to drive with a P0520 code?
Only once you know the real oil pressure is good. Check the oil level, listen for ticking or knocking, and confirm pressure with a mechanical gauge. If the red oil warning is on or the engine is noisy, stop the engine and do not drive it.
Does P0520 mean my oil pressure is low?
Not necessarily. P0520 is a circuit fault, and the sensor, connector or wiring is often to blame. But a faulty circuit can also hide real low pressure, so the only way to be sure is to test with a mechanical oil pressure gauge.
Can a leaking oil pressure sensor cause P0520?
Yes. A sensor that leaks internally can push oil into its electrical connector and even along the wires, which disturbs the signal. Replace the sensor and clean or replace the contaminated connector, or the fault can return.
What is the difference between P0520 and P0524?
P0520 is an electrical fault in the oil pressure sensor circuit. P0524 means the engine computer has measured oil pressure that is actually too low. P0524 is the more urgent of the two, but both call for a mechanical pressure check.
How much does it cost to fix P0520?
Roughly $50 to $300 installed for an oil pressure sensor or switch, $20 to $200 for a connector, and $50 to $300 for a wiring repair. A mechanical oil pressure test typically costs $50 to $150 and is worth doing first.
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