The oil pressure sensor circuit is faulty — always check actual oil pressure first with a mechanical gauge before condemning parts.
P0520 — also written PO52O, P 0520, 0520 — is the OBD-II code for engine oil pressure sensor/switch circuit. Same code, same fix: this page covers every spelling of it.
This code means the ECU isn't happy with the signal from the oil pressure switch, often seen on high-mileage Insignias and N47 BMWs where the sensor has either leaked internally or the engine is physically losing pressure.
P0520 is a electrical fault code, typically costing £45–£500 to put right in a UK garage.
What P0520 actually feels like to drive
- The 'red oil can' lamp flickering only when the engine is hot and idling at traffic lights.
- A 'Low Oil Pressure - Stop Engine' warning that disappears as soon as you touch the throttle.
- The car 'chimes' at you every time you take a sharp roundabout.
- Engine sounds like a 'bag of nails' or a sewing machine for a few seconds on a cold start.
- The oil light doesn't come on at all when you first turn the ignition to 'on' (bulb/circuit check failure).
What causes P0520?
- Failed oil pressure sensor (common on BMW N47 and Vauxhall A20DTH)
- Wiring fault
- Genuinely low oil pressure
UK vehicles that throw P0520 most often
- Vauxhall Insignia 2.0 CDTi (A20DTH) 2009-2015
- BMW 3 Series 2.0d (N47) 2007-2014
- Ford Transit Custom 2.2 TDCi 2012-2016
- Jeep Grand Cherokee 3.0 CRD 2011-2018
- Audi A4 2.0 TFSI (EA888) 2008-2015
- Fiat 500 1.2 Petrol 2008-2020
How P0520 is fixed
- Verify with mechanical gauge FIRST
- Replace oil pressure switch
- If real pressure is low, stop driving
The P0520 misdiagnosis that wastes money
I see lads in the trade diving straight for a new oil pump or a cheap Euro Car Parts sensor the second they see this code. On the Vauxhall A20DTH engines (Insignia/Zafira), they often ignore the real killer: the oil pickup pipe seal. They swap the sensor, the light stays off for ten minutes, and then the bottom end lets go on the A9. The sensor itself is often fine; it's the wiring loom rubbing near the starter motor or a genuine lack of pressure that's the culprit. Don't throw a £15 part at it until you've proven the engine isn't starving.
What a UK garage should charge for P0520
For a basic sensor swap on something like a Corsa, you're looking at £45-£80 including a decent Delphi or Bosch part. However, a proper diagnostic with a mechanical pressure test will cost you 1 hour of labour (roughly £60-£90 depending on where you are in the UK). If it turns out to be the dreaded Insignia pickup seal, you're looking at £400-£500 because the sump has to come off. Main dealers will easily double these prices, charging £150 just to plug their tablet in.
P0520 repair cost in the UK
Most P0520 repairs land between £45–£500 including parts and labour. The spread is wide because the cheap fix (a sensor, a hose, a leak) and the expensive fix (a major component) throw the same code — which is why a proper diagnosis before parts are bought saves the most money.
Bob's tip on P0520
If you take this to a garage, tell them straight: "I want a mechanical oil pressure test performed before you fit any parts." A proper tech will hook up a manual gauge to the block to see what the PSI actually is. If they just want to swap the sensor and send you on your way, walk away. Also, if you're in a BMW N47, check the sensor connector for oil wicking. The oil can actually push through the sensor and travel up the wires into the ECU, which turns a £60 fix into a £1,200 nightmare if you catch it too late.
Can you drive with P0520?
Stop and check oil level immediately.
Urgency: high.