P0520 fault code: Engine Oil Pressure Sensor/Switch Circuit Low severity

P0520 means “Engine Oil Pressure Sensor/Switch Circuit” — a vehicle speed & idle control fault in the powertrain. Safe to drive in most cases; stalling in traffic is the main safety concern. Typical UK repair cost: £25–£300 depending on the underlying cause.
LowSeverity
P05xxVehicle Speed & Idle Control
£25–300Typical UK repair cost
MOT fail riskif the warning light stays on

What does P0520 mean?

P0520 is a generic (SAE standard) powertrain code reported by your car’s engine control unit. It sits in the P05xx block, which covers vehicle speed & idle control. The stored description is “Engine Oil Pressure Sensor/Switch Circuit”. The code itself tells you which circuit or system tripped the fault — not always the exact part that failed, which is why a short diagnosis pays for itself before replacing components.

Symptoms you may notice

  • Idle speed too high, too low, or hunting up and down
  • Stalling when coming to a stop
  • Cruise control not engaging

Most common causes

  1. Carbon-clogged throttle body or idle control valve
  2. Vacuum leak around the intake manifold
  3. Faulty vehicle speed sensor
  4. Throttle pedal or position sensor fault

How to diagnose P0520 yourself

  1. Clean the throttle body with throttle-safe cleaner
  2. Check for vacuum leaks with the engine warm
  3. Scan live throttle position and idle valve duty data
Tools that read and clear P0520

A basic code reader confirms the fault; a full-system scanner shows the live data you need for the steps above.

Will P0520 fail an MOT?

Not directly tested at MOT, but if the fault keeps the engine management light on, that light alone is a Major defect and a fail.

Before booking your test, check what usually fails on your car: see our MOT pass rates by make and model, built from 33.1 million DVSA tests.

Typical UK repair costs

OutcomeTypical cost (parts + labour)
DIY: read code + basic checks£0 (scanner assumed)
Independent garage diagnosis£30–£60
Typical repair range for this fault£25–£300
Main dealer equivalent£37–£540

Costs are indicative UK ranges for independent garages in 2026. Main dealers typically charge 40–80% more.

Diagnose the symptom, then price the repair

Car diagnostic test cost UK (2026): scan vs actual diagnosis£40–£100 is typical for an independent first assessment — but a code read is not the same as finding the cause.
P0500Vehicle Speed Sensor 'A' P0501Vehicle Speed Sensor 'A' Range/Performance P0502Vehicle Speed Sensor 'A' Circuit Low Input P0503Vehicle Speed Sensor 'A' Intermittent/Erratic/High P0504Brake Switch 'A'/'B' Correlation P0505Idle Air Control System P0506Idle Air Control System RPM Lower Than Expected P0507Idle Air Control System RPM Higher Than Expected

P0520 — quick answers

Is it safe to drive with P0520?

Safe to drive in most cases; stalling in traffic is the main safety concern.

Will P0520 clear itself?

If the underlying fault stops occurring, most ECUs extinguish the light after around 40 healthy warm-up cycles — but the code stays stored as history. Fix the cause, clear it with a scanner, then confirm it stays away over a full drive cycle.

How much does it cost to fix P0520 in the UK?

Typically £25–£300 at an independent garage depending on which cause you confirm. Diagnosing it yourself with a scanner avoids a £30–£60 diagnostic fee and stops parts being replaced on guesswork.

Will P0520 fail my MOT?

Not directly tested at MOT, but if the fault keeps the engine management light on, that light alone is a Major defect and a fail.

Code definitions follow the SAE J2012 standard. MOT defect rules reflect the DVSA MOT inspection manual (2026). This page is general guidance for UK drivers, not a substitute for a professional diagnosis.