Motor Vehicle Expert
OBD fault code guide

P0520 Code Meaning UK

P0520 means “Engine Oil Pressure Sensor/Switch Circuit”. In plain English, the engine computer is not happy with the oil pressure sensor signal. It may be a faulty sensor, damaged wiring or connector issue, but this code must be treated carefully because real low oil pressure can cause serious engine damage.

📅 Updated June 2026 🇬🇧 UK diagnostic guide 🛠 Oil pressure circuit fault
Quick answer Fault codes hub Oil warning guide
✓ P0520 meaning ✓ Oil pressure checks ✓ UK repair costs ✓ Safety-first advice
Quick answer Meaning Symptoms Causes Diagnosis Oil pressure checks Repair costs Can you drive? MOT impact Related guides FAQs
Quick answer

What does P0520 mean?

P0520 means the ECU has detected an abnormal signal from the engine oil pressure sensor or switch circuit. The fault may be electrical, such as a failed sensor, broken wire or corroded connector. However, because oil pressure protects the engine, the oil level and real oil pressure must be checked before assuming it is only a sensor problem.

Most likely area

Oil pressure sensor, wiring, connector, oil level, oil grade, oil pump, blocked pickup or real low oil pressure.

Urgency

High if the oil warning light is red, oil level is low, engine is noisy or pressure is genuinely low.

MOT risk

Can affect warning lights, oil leaks, smoke, emissions and running condition.

Code meaning

P0520 — Engine Oil Pressure Sensor/Switch Circuit

The full description is usually P0520 Engine Oil Pressure Sensor/Switch Circuit. It means the signal from the oil pressure sensor circuit is not what the ECU expects. The signal may be too high, too low, missing, intermittent or implausible.

Some vehicles use a simple oil pressure switch, while others use a pressure sensor that reports a changing value. Either way, the system is there to protect the engine from running with unsafe oil pressure.

Mechanic view

Why P0520 must be treated differently

Many fault codes let you keep driving carefully while you book a repair. Oil pressure codes are different. If the warning is caused by real low oil pressure, continuing to drive can damage bearings, turbochargers, timing chains and the engine itself.

A sensor fault is common, but you only call it a sensor fault after confirming the oil level and actual pressure are safe.

Symptoms

Common symptoms of a P0520 code

P0520 can appear with only an engine light, but serious oil pressure symptoms should never be ignored.

Engine management light

A steady engine warning light may appear with P0520 stored.

Oil warning light

A red oil pressure warning light is urgent and should not be ignored.

Oil pressure message

Some cars display “low oil pressure” or similar dashboard warnings.

Engine ticking or knocking

Noise from the engine can indicate poor lubrication and possible real low pressure.

Oil leak

Leaks around the sensor or engine can reduce oil level or contaminate the connector.

No obvious symptoms

If the sensor circuit alone is faulty, the engine may seem to run normally.

Common causes

What causes a P0520 fault code?

P0520 can be caused by an electrical sensor issue or a genuine engine oil pressure problem.

Very common

Faulty oil pressure sensor

The sensor or switch can fail internally and send an incorrect signal.

Wiring

Damaged sensor wiring

Oil, heat, vibration or previous repairs can damage the wiring near the sensor.

Connector

Oil-contaminated connector

Oil leaking through or around the sensor can contaminate the plug and pins.

Basic check

Low engine oil level

Low oil level can reduce pressure and trigger warnings.

Oil issue

Wrong oil grade or poor oil condition

Incorrect or badly degraded oil can affect pressure and sensor readings.

Serious

Oil pump problem

A weak or failing oil pump can cause real low oil pressure.

Restriction

Blocked oil pickup

Sludge or debris can restrict oil flow to the pump.

Engine wear

Internal engine wear

Worn bearings or internal clearances can reduce actual oil pressure.

Electrical

Poor earth or ECU signal fault

Electrical issues can corrupt the oil pressure signal.

Diagnosis

How a garage should diagnose P0520

✅ Check the engine oil level before anything else.

✅ Do not run the engine if there is a red oil pressure warning and engine noise.

✅ Scan all stored, pending and permanent codes.

✅ Inspect the oil pressure sensor and connector for oil contamination.

✅ Check wiring for damage, corrosion or poor connection.

✅ Confirm whether the sensor signal changes with engine running.

✅ Fit a mechanical oil pressure gauge if real pressure is in doubt.

✅ Check oil grade, service history and sludge concerns.

✅ Investigate oil pump, pickup or internal engine faults if pressure is genuinely low.

Avoid this mistake

Do not assume the sensor is lying

A failed oil pressure sensor is common, but assuming the sensor is lying can be an expensive mistake. If oil pressure is genuinely low, the engine may be at risk every second it is running.

The safest confirmation is a proper oil pressure test with a gauge where needed.

Oil pressure safety checks

Mechanic-style checks for P0520

A proper P0520 diagnosis should separate a sensor/circuit fault from real low oil pressure before the car is driven normally.

Oil level first

Check level on the dipstick or electronic level system before running the engine further.

Warning colour

A red oil pressure warning is more urgent than a stored code with no warning light.

Engine noise

Ticking, knocking or rattling with oil pressure warning is a stop-driving situation.

Sensor leak

Oil pressure sensors can leak and contaminate their own connector.

Mechanical gauge

A gauge test confirms whether oil pressure is genuinely safe.

Oil condition

Sludge, wrong oil or overdue servicing can affect pressure and oil flow.

UK repair cost guide

How much does P0520 cost to fix in the UK?

Costs vary depending on whether the fault is a sensor, wiring issue, oil service problem or genuine oil pressure fault. These are rough UK guide prices only.

Diagnostic scan and oil check

Usually around £40–£120 depending on testing depth.

Oil pressure sensor replacement

Often moderate if access is simple, but some sensors are awkward to reach.

Wiring or connector repair

Cost depends on oil contamination, corrosion and loom access.

Oil and filter service

May help if poor oil condition or wrong oil grade is contributing.

Mechanical pressure test

May cost extra but is valuable if real oil pressure is uncertain.

Oil pump or engine repair

Can be expensive if genuine low pressure is caused by pump, pickup or internal wear.

Safe driving advice

Can you drive with a P0520 code?

Be careful. If P0520 appears with a red oil pressure warning, low oil level, engine ticking, knocking, rattling, oil leak or “stop engine” message, stop driving immediately. If the car only has a stored code and the oil level and pressure are confirmed safe, short careful driving may be possible while arranging repair.

✅ Lower risk: stored code only, oil level correct, no oil light, no engine noise and normal running.

⚠️ Medium risk: intermittent warning, oil leak near sensor, unknown pressure or repeated warning light.

🚫 High risk: red oil light, low oil level, engine noise, low pressure message or visible major oil leak.

Real experience

What I would check first

On a real P0520 job, I would check the oil level and listen to the engine before worrying about scanners. If the oil light is red and the engine is noisy, I would not keep it running.

If the engine sounds normal and oil level is correct, I would inspect the oil pressure sensor and connector. Leaking sensors and oil-soaked plugs are common, but I would still confirm pressure if there is any doubt.

MOT implications

Will P0520 fail an MOT?

P0520 can lead to an MOT failure if it causes warning lights, visible oil leaks, excessive smoke, poor running or safety concerns. A serious oil leak or engine condition that affects safe operation should be repaired before the vehicle is presented for MOT.

Oil warning light

Oil pressure warnings should be treated seriously before MOT.

Visible oil leak

Oil leaks can affect MOT outcome depending on severity and location.

Engine condition

Smoke, rough running or serious engine noise should be investigated before testing.

Oil Warning Light Guide Can Oil Leak Fail MOT?
Back to main hub

Browse more OBD fault code guides

P0520 is one common engine oil pressure sensor and oil pressure circuit diagnostic trouble code. For more common codes, meanings, symptoms, repair costs and MOT implications, use the main Motor Vehicle Expert fault-code hub.

Back to OBD Fault Codes Hub Use Diagnostic App
Frequently asked questions

Frequently Asked Questions About P0520

Find answers to common questions about P0520 oil pressure sensor faults, oil warning lights, driving safety, repair costs and MOT implications.

What does P0520 mean?

P0520 means the engine computer has detected a fault in the engine oil pressure sensor or switch circuit. It may be a sensor or wiring issue, but real low oil pressure must be ruled out first.

Can I drive with a P0520 code?

Be very careful with P0520. If the red oil pressure light is on, oil pressure warning appears, the engine is noisy, or oil level is low, stop driving immediately because real low oil pressure can destroy the engine.

Will P0520 fail an MOT?

P0520 can lead to an MOT failure if it causes an engine warning light, oil warning light, visible oil leak, excessive smoke, poor running or any condition that affects safety or emissions.

What causes a P0520 code?

Common causes include a faulty oil pressure sensor or switch, damaged wiring, corroded connector, low oil level, wrong oil grade, blocked oil pickup, oil pump issue, poor engine earth or real low oil pressure.

How much does P0520 cost to fix in the UK?

A diagnostic check may cost around £40 to £120. Oil pressure sensor replacement may be moderate if access is simple, while real oil pressure faults, oil pump work or internal engine diagnosis can cost much more.

Is P0520 always just a faulty sensor?

No. P0520 can be caused by a faulty sensor, but real oil pressure problems must be ruled out before assuming the sensor is wrong.

About this guide

Based on practical mechanic-style diagnostic experience

Motor Vehicle Expert publishes practical UK vehicle guidance based on real-world mechanical knowledge and hands-on diagnostic experience. This P0520 guide is written to help drivers understand oil pressure sensor circuit faults while treating possible real low oil pressure seriously.

Fault codes should always be treated as a starting point for diagnosis. If your car has a red oil warning light, low oil level, engine knocking, ticking, rattling or a stop-engine message, stop driving and get professional help immediately.