OBD-II trouble code
P0520: Engine Oil Pressure Sensor/Switch Circuit
The catch-all circuit fault for the oil pressure sensor — the PCM has detected a general problem with the sensor circuit that doesn't land cleanly in the low (P0522) or high (P0523) bucket. Verify real oil pressure before you decide the sensor is the fault. A pump that is not making pressure stores the same code.
Quick facts
- System
- Powertrain
- Category
- Electrical / PCM
- Severity
- High severity
- Drivable
- Usually safe to drive short-term
- Repair cost range
- $50 – $1,500
- DIY difficulty
- Intermediate DIY
Browse every code in P0500–P0599, or start from the full code library.
What does P0520 mean?
P0520 is the general circuit-malfunction code for the engine oil pressure sensor or switch. Where P0522 and P0523 describe a signal pinned specifically too low or too high, P0520 is the broader fault the PCM sets when it sees the oil pressure circuit misbehaving in a way that doesn't fit neatly into either of those — an erratic signal, a reading that doesn't change when it should, or a circuit fault the PCM flags generically. The sensor is a three-wire device — 5V reference, signal, and ground — that outputs a voltage scaling with oil pressure, and P0520 means the PCM no longer trusts what that circuit is telling it.
Verify actual oil pressure with a mechanical gauge before you decide the sensor is at fault. A failed sensor and a failed pump can store the same code. If the cause is low oil pressure from a failing pump, a clogged pickup screen, or a low oil level, continuing to drive can destroy the engine in minutes. If a warning light or a gauge drop comes with the code, pull over, shut down, check the oil level, and confirm pressure with a mechanical gauge before driving again.
Once the gauge shows the pressure this engine's chart calls for, test the sensor and its wiring. Connectors corrode where the sensor sits in oil seepage and road grime. On a GM Vortec V8 the drawing is what places this sender. It may be in the valley, on the oil-filter adapter, or in the block, and those are different mounts. Chrysler Hemi, Ram, and various diesels see this code from heat-fouled or oil-fouled connectors near the block.
Because this is the generic circuit code rather than a steady high or low, include a wiggle test of the connector and harness before the sensor is replaced.
Common causes
- Failed oil pressure sensor/switch — test it after a mechanical gauge has shown the pressure the chart calls for
- Corroded sensor connector from oil seepage or road grime
- Intermittent or chafed wiring in the harness near the sensor or block
- Pushed-back or broken terminal in the sensor connector
- Open or shorted 5V reference or signal-return circuit
- Genuine low oil pressure from a worn pump or clogged pickup — rule it out with a gauge before the sensor is blamed
- Genuine low oil pressure from very low oil level
- PCM internal fault affecting the sensor circuit (rare)
Symptoms
- Check engine light on with P0520 stored
- Oil pressure gauge reading erratically or sitting at an implausible value
- Oil pressure warning light on or flickering
- The engine can sound normal with a circuit fault and with pressure that is low but not yet knocking. Noise means stop. Silence does not identify the sensor
- On real low-pressure cases: lifter tick, rod knock, or warning light staying on after start
Diagnostic steps
- 1.If a warning light or abnormal gauge reading is present, pull over and shut down. Check the oil level on the dipstick and add oil if low — never keep running a verified low-pressure condition.
- 2.Listen to the engine. Lifter tick, rod knock, or any unusual noise means stop. A quiet engine is a reason to fit the gauge, not a reason to call it the sensor.
- 3.Plumb a mechanical oil pressure gauge into the sender port and compare it with the specification for this engine, hot, at the sensor. There is no 20–40 psi hot-idle band that fits the family. A 2008 Chevrolet Impala 5.3L chart lists minimum hot oil pressure of 6 psi at 1,000 rpm, 18 psi at 2,000 rpm and 24 psi at 4,000 rpm. Ten psi at a hot idle is inside that chart. GM bulletin 24-NA-173 uses a hot-idle reading below 20 psi at the sensor port as a stuck relief-valve screen on listed 2019–2024 L84 and L87 trucks, after the sensor circuit is cleared. That 20 psi figure is a failure screen for those engines, and the bulletin says a reading at the oil filter can differ from the sensor port by as much as 10 psi.
- 4.Inspect the sensor connector for green corrosion, oil contamination, or pushed-back pins; clean or repair as needed.
- 5.Do a wiggle test on the connector and harness while watching live data — P0520 being the generic code, an intermittent connection is a real possibility.
- 6.Check the 5V reference and ground at the sensor connector (key on, engine off). Trace any missing reference back toward the PCM.
- 7.On a GM Vortec truck, open the diagram before the manifold is planned. Valley mounting means the intake moves. A filter-adapter mount, or a block mount, does not.
- 8.After replacing the sensor, clear the code, confirm the gauge reads correctly, and verify no other oil-system codes set.
Repair cost
$50 – $1,500
A connector you can reach without lifting a manifold is the small repair. An oil pump, or engine work after the engine was run with no pressure, is the large one. Treat the printed low and high as a planning span, not a price on a work order. Add the sensor or the pump to the labor time published for this vehicle. Look the sensor up on the diagram before you assume an intake has to come off. A mechanical gauge comes before either repair.
Estimate your repair
Run the numbers for your vehicle
Open the Repair Cost Estimator with oil pressure sensor / switch replacement preselected. Adjust labor rate and vehicle category to fit your situation.
DIY vs shop
This is an intermediate DIY job. It usually involves diagnostic steps, specialty parts, and some careful work in tight spaces. If you have the tools and a service manual or trustworthy video for your specific vehicle, it is achievable in a weekend. Otherwise, a competent independent shop will be faster.