P0520 code: Engine Oil Pressure Sensor/Switch Circuit
P0520 means engine Oil Pressure Sensor/Switch Circuit. The code says where to look, not what failed — the fix depends on which cause your car actually has.
What P0520 means
P0520 means the computer sees a general fault in the oil pressure sensor (sender) circuit — the signal is out of the expected range or behaving implausibly, without pinning down 'low' (P0522) or 'high' (P0523) specifically. In most cases the problem is the sender itself, its connector, or the wiring: these sensors live on the hot, oily side of the engine and commonly fail or leak internally with age. The critical caveat is that your oil pressure warning system is now untrustworthy — the gauge or light may read wrong in either direction — so you must verify oil level immediately and confirm actual pressure before assuming it's just electrical. A shop does this by threading a mechanical gauge into the sender's port; good mechanical pressure means you can fix the circuit at leisure, while low mechanical pressure turns this into an urgent engine problem. Never dismiss an oil pressure code on faith.
P0520 symptoms
- Oil pressure gauge reading erratic, zero, or pegged high
- Oil pressure warning light on or flickering (possibly falsely)
- Check-engine light
- Usually no change in how the engine runs
- Sometimes oil seepage around the sender
What it costs to fix P0520
Typical range: $50–$250 · about ~0.3–1 hrs of labor
| If the cause is… | Part | Labor |
|---|---|---|
| Oil pressure sender replacement | $20–$100 | ~0.3–1 hrs |
| Wiring / connector repair | $5–$80 | ~0.3–1 hrs |
| Mechanical oil pressure verification | $0–$0 | ~0.5–1 hrs |
The sender is a cheap part; cost depends on how reachable it is — some are right on top, others hide behind the intake or exhaust. The mechanical pressure check is worth its labor: it's what separates a cheap sensor swap from a serious engine diagnosis.
The price swings on which cause it turns out to be — so confirm the cause before paying. Diagnose P0520 for my exact vehicle →
How to fix P0520
Easy — basic tools, most owners can do this
- Check the oil level and listen at idle
Before anything electrical, pull the dipstick on level ground and top up if needed, then idle the engine and listen for ticking or knocking that wasn't there before. With the sender circuit faulted, the dash light or gauge can't be trusted in either direction, so the dipstick and your ears are the only reliable warning for now.
- Look for oil weeping from the sender or in its plug
Find the sender — commonly near the oil filter, on the side of the block, or under the intake on some V engines — and inspect it. A sender that leaks internally pushes oil into its connector and can wick it up the wire toward the computer; an oil-soaked plug or a wet sender body all but confirms the part has failed.
- Identify the sender type and check its circuit
A single-wire switch only works the dash light, closing to ground when pressure is low, while a three-wire sensor gets a reference (usually 5 volts), a ground, and returns a variable signal. With the key on, check that the reference and ground are present at the harness; a missing one means the fault is upstream of the sender.
- Confirm real pressure with a mechanical gauge
Remove the sender, thread a mechanical gauge into its port with the correct adapter, and read pressure at a warm idle and at raised RPM against the spec for your engine. Good numbers mean the engine is healthy and the fault is electrical; low numbers turn this into an engine problem that needs attention before any more driving.
- Replace the sender and confirm the reading tracks RPM
Fit a quality sender with the thread sealant the manufacturer specifies and snug it without overtightening, since the bodies crack. Clear the code, then check that the gauge or oil pressure value rises with engine speed and the warning light goes out promptly after start-up.
DIY or shop? A home mechanic can handle most P0520 cases: checking the level, cleaning or replacing the connector, and swapping a sender that sits near the filter or on the side of the block. The mechanical gauge test is worth paying for if you don't own a gauge and adapter set — it is the only thing that separates a cheap sensor fault from a failing engine. It becomes shop work when the sender sits under the intake manifold, or when oil has wicked deep into the harness and needs repair beyond the plug.
Tools for the DIY steps: Oil pressure sender socket · Mechanical oil pressure gauge with adapters · Digital multimeter · Thread sealant specified for the sender · Electrical contact cleaner · Shop rags and a drip pan
Not sure which step applies to your car? Get the likely cause for your exact vehicle before buying anything for P0520.
Start a case with P0520 and your car. Redline weighs these causes against what your car shows, and names the check that would settle it before you buy parts.
Can I drive with P0520?
Redline can’t determine from a symptom or code alone whether your car is safe to drive.
P0520: common questions
Is P0520 just a bad sensor or real low oil pressure?
Usually the sender or its wiring — but you can't know from the code alone, and the price of guessing wrong is an engine. Check the oil level now, listen for ticking or knocking, and have actual pressure confirmed with a mechanical gauge before writing it off as electrical.
Can I keep driving with P0520?
Redline can't tell from the code alone whether your engine has real oil pressure. Check the oil level and listen for new engine noise, and get it inspected promptly. Your pressure warning system is currently unreliable — so if the red oil light comes on or you hear new engine noise, stop immediately.
How does a shop confirm whether the sensor is lying?
By removing the sender and threading a mechanical gauge into the same port, then reading pressure directly at idle and at higher rpm. If mechanical pressure is in spec while the electrical reading is nonsense, the sender or circuit is confirmed as the fault.
How is P0520 different from P0522 and P0523?
All three are sender-circuit codes. P0520 is the generic 'circuit fault' version, P0522 means the circuit voltage is specifically low, and P0523 means it's specifically high. None of them, by themselves, prove the engine's actual oil pressure is bad — that always needs mechanical verification.
Symptoms that trigger P0520
Drivers who get this code often notice one of these. Each has its own causes and cost guide:
Related trouble codes
Don’t have a scanner yet? A ~$25 Bluetooth adapter reads codes like P0520 from your phone. See our guide to the best OBD2 Bluetooth adapters. Run a repair shop? See Redline for shops.
Generic OBD-II reference. Manufacturer-specific behavior varies. Confirm with a scan tool and, for safety-related codes, a professional inspection. Cost ranges are reference ranges, not quotes.
Seeing P0520 on your car?
Every problem becomes a Case. Tell Redline what the car is doing: it shows what the evidence supports, what’s still missing, and what to check next, before you approve a repair.
“Inner pad ~1 mm. Outer pad 3 mm.”
Next: check the slide pins move freely before buying parts.