P0521 on 2013-2020 Buick Encore: Engine Oil Pressure Sensor Causes and Fixes

What's Unique About the 2013-2020 Buick Encore

The 1.4L Ecotec (LUV) engine in the Buick Encore is known for a few specific issues that can lead to code P0521. A very common problem is the failure of the PCV diaphragm in the valve cover, which can cause high oil consumption and a vacuum leak. If the oil level drops too low, it will trigger a legitimate low oil pressure condition and set this code. Additionally, these engines are sensitive to the type of oil and filter used; using oil that doesn't meet the GM dexos1 specification or a low-quality filter can cause pressure-related problems, sometimes immediately after an oil change. GM has also noted in TechLink articles that ice or sludge can form in the PCV system in extremely cold weather, leading to pressure issues and codes like P0521. GM has issued service bulletins (like #A202302140) regarding failing oil pumps that can get stuck and cause this code, sometimes accompanied by P06DD or P06DE. Manufacturer TSB #PIP4786C also provides guidance for technicians encountering a "Low Oil Pressure" message alongside P0521, emphasizing the need to follow published service information when scan tool data indicates low pressure.

Symptoms You May Notice

• Check Engine Light is on
• Oil pressure warning light on the dashboard
🎬 Watch: Diagnosing an oil pressure light on the 1.4L engine
• Oil pressure gauge reading abnormally high, low, or fluctuating erratically
• Engine running rough or making ticking/knocking noises (if actual oil pressure is low)
• Engine may stall
• Oil leaking from the oil pressure sensor onto the electrical connector

Most Likely Causes

1. Faulty Engine Oil Pressure Sensor 🔴 High Probability The sensor is a very common failure point on many GM vehicles. It is exposed to significant heat and vibration, which can cause internal failure or oil leaks through the sensor body into the electrical connector. The ECM can be sensitive to non-OEM sensors, so using a genuine ACDelco part is often recommended.
   How to confirm: With the engine running, if the scan tool shows an erratic or stuck oil pressure reading but a mechanical gauge shows normal, steady pressure, the sensor is bad. Inspect the sensor's electrical connector for oil contamination, which is a sign of internal failure.
   Typical fix: Replace the engine oil pressure sensor and the small filter screen beneath it. The sensor is located on the engine block, often behind the A/C compressor. 🎬 See this walkthrough for replacing the oil pressure sensor
   Est. part cost: $25-$80
2. Low Engine Oil Level 🔴 High Probability The 1.4L Ecotec can consume oil, often due to a common PCV system failure in the valve cover, which leads to a vacuum leak and increased consumption. This is a well-documented issue for this engine.
   How to confirm: Check the engine oil dipstick. If the level is below the minimum mark, this is the likely cause.
   Typical fix: Top up the engine oil to the correct level with full synthetic oil meeting the GM dexos1 specification. Investigate the cause of oil loss, such as a failed PCV valve/valve cover. 🎬 Watch: How to replace the valve cover and PCV system
   Est. part cost: $10-$70
3. Incorrect Oil or Clogged Oil Filter 🟡 Medium Probability These engines require a specific oil viscosity (full synthetic dexos1) and are sensitive to oil filter quality. Using the wrong oil or a cheap, restrictive aftermarket filter can impede flow and trigger P0521, sometimes right after an oil change. Some forum users report that switching to a specific high-quality filter like the Mobil 1 M1-113A resolved their recurring P0521 code.
   How to confirm: Verify the type of oil and filter used during the last service. If incorrect, this is a probable cause. A restricted filter may cause a pressure drop; replacing just the filter can sometimes show an immediate improvement on a mechanical gauge.
   Typical fix: Perform an oil and filter change using the correct GM-specified full synthetic oil and a high-quality filter (such as ACDelco PF64 or equivalent).
   Est. part cost: $40-$80
4. Clogged Oil Pressure Sensor Filter Screen 🟡 Medium Probability
   How to confirm: This is typically found during the replacement of the oil pressure sensor. The screen will be visibly clogged with sludge. A partially obstructed screen was noted by an owner as a fix.
   Typical fix: Remove and replace the filter screen. It is highly recommended to replace this part whenever the oil pressure sensor is replaced.
   Est. part cost: $5-$15

Rare But Worth Checking

• Failing Oil Pump: While less common, GM has issued service bulletins (e.g., #A202302140) for some vehicles that mention the oil pump as a potential cause for P0521, sometimes accompanied by P06DD or P06DE. This is a serious issue that results in genuinely low oil pressure.
• Worn Internal Engine Components: In high-mileage engines, worn main bearings or camshaft bearings can cause excessive clearances, leading to a drop in overall oil pressure that the sensor correctly reports. This is a worst-case scenario requiring major engine repairs.
• Wiring Harness Issue: A damaged wire or loose/corroded connection in the circuit between the oil pressure sensor and the ECM can cause the signal to be lost or erratic, triggering the code. The harness is near the hot exhaust, making it susceptible to damage.

Diagnosis Steps

1. Check the engine oil level and condition immediately. If the level is low, top it off with the correct dexos1-spec oil and see if the code clears. Note any signs of sludge.
2. Connect a professional scan tool to view live data from the oil pressure sensor with the engine running. Note if the reading is stuck, erratic, or zero.
3. CRITICAL STEP: Verify the actual engine oil pressure. Remove the oil pressure sensor and connect a mechanical oil pressure gauge.
4. Start the engine and compare the reading on the mechanical gauge to the manufacturer's specifications at idle and higher RPMs (e.g., GM specs might be ~22 psi @ idle, 55-94 psi @ 3000-3500 RPM).
5. If the mechanical gauge shows good, steady pressure but the scan tool showed an erratic reading, the oil pressure sensor is faulty and should be replaced.
6. When replacing the sensor, be sure to also remove and replace the small filter screen located in the port beneath it.
7. If the mechanical gauge shows low or no oil pressure, do not run the engine. The problem is more severe, potentially a failing oil pump, clogged oil pickup tube, or worn internal engine components. Further mechanical diagnosis is required.
8. Inspect the wiring and connector for the oil pressure sensor for any signs of damage, corrosion, or oil contamination. Repair as needed.

Parts You'll Likely Need

• Engine Oil Pressure Sensor (OEM #12673134) — This is the most common part to fail and cause erratic or incorrect readings that trigger code P0521.
  Trusted brands: ACDelco, Delphi
  OEM price range: $40-$70
  Aftermarket price range: $25-$50
• Engine Oil Pressure Sensor Filter (OEM #12634025) — This small screen under the sensor can get clogged with sludge, causing a false low-pressure reading at the sensor. It's inexpensive and should always be replaced with the sensor.
  Trusted brands: ACDelco, Dorman
  OEM price range: $5-$15
  Aftermarket price range: $5-$10
• Engine Oil Pressure Sensor Connector — A poor connection at the sensor will cause erratic readings and trigger P0521. Oil leaking through a failed sensor can also contaminate and ruin the connector.
  Trusted brands: ACDelco, Dorman
  OEM price range: $40-$60
  Aftermarket price range: $20-$45

Related Codes That Often Appear With This One

• P0171 — A failed PCV system in the valve cover creates a vacuum leak, which can set a P0171 (System Too Lean) code. This PCV failure also leads to high oil consumption, which can then cause P0521 if the oil level drops too low.
• P0520 — P0520 indicates a fault in the oil pressure sensor circuit itself, while P0521 points to a performance/range issue. They are closely related and can appear together.
• P0522 / P0523 — These codes indicate the sensor signal voltage is specifically too low (P0522) or too high (P0523), while P0521 indicates a general performance problem. They all point to a fault within the same system.
• P06DD / P06DE — These codes, indicating the oil pressure control solenoid is stuck off or on, are specifically mentioned in GM service bulletins as companion codes to P0521 when there is an oil pump issue.

Technical Service Bulletins (TSBs) & Recalls

• A202302140: Mentions failing oil pumps as a potential cause for P0521. This bulletin notes that the engine oil pump may be stuck due to foreign material, and dealers are instructed to perform an engine oil pump screening test.
• Bulletin #A202302140 01: A service update stating that on certain vehicles, the engine oil pump may be stuck due to foreign material, potentially setting DTCs P0521, P06DE, and P06DD.
• PIP5152D: Discusses diagnosis for P0521, P06DD, and P06DE, pointing towards potential oil pump issues.
• PIP4786C: Provides information regarding vehicles that may display a "Low Oil Pressure" message and set code P0521 in the ECM.
• GM TechLink (Cold Weather): Notes that in extremely cold conditions, ice can form in the crankcase ventilation system on the 1.4L LUV engine, leading to pressure issues and P0521.
• Note on Encore GX TSBs: While not for this specific model, TSBs for the newer Encore GX (A222379710, A222379711) show a history of GM dealing with P0521-related software and hardware issues, such as an ECM glitch preventing the code from clearing.

Platform-Specific Known Issues

• A known issue on the 1.4L Ecotec is the failure of the PCV check valve in the valve cover, leading to high oil consumption and potentially this code if the oil level gets too low.
• GM issued a voluntary emission recall (A222379711) for some 2020 Encore GX models where the ECM would not properly clear the permanent status of a P0521 code, potentially causing failed emissions tests. This required an ECM reprogram.

Mechanic-Grade Diagnostic Values

• Engine Oil Pressure (Mechanical Gauge, Hot Engine) — expected: ~22 PSI at idle; 55-94 PSI at 3000-3500 RPM.. Failure: Pressure significantly below these ranges indicates a mechanical issue (pump, bearings, pickup tube).
• Engine Oil Pressure Sensor Signal Voltage — expected: Varies with pressure, typically ~1.3V at hot idle. The normal operating range is between 0.5V (low pressure) and 4.5V (high pressure).. Failure: The ECM may set P0521 if the voltage is less than 0.1V or greater than 4.4V for more than 10 seconds, or if the voltage is stuck.

Hidden / Shadow Codes Worth Checking

• Permanent DTC P0521: This is not a separate code, but a status. On some 2020-2023 Encore GX models (which have a different engine but illustrate a GM-specific issue), the ECM may fail to clear the *permanent* status of P0521 even after a successful repair. This will not illuminate the MIL but will cause an emissions test failure. (see via This status is visible with professional scan tools. GM issued a recall (A222379710 / A222379711) to fix this with an ECM software update at the dealer.)

Scan Tool Commands That Help

• GDS2 (GM Dealer Scan Tool): Engine Oil Pump Screening Test — This is a specific procedure outlined in GM Service Bulletin #A202302140 for when P0521 is present with P06DD or P06DE. The tech runs the engine through a series of RPM cycles (e.g., 2,000 RPM for 30s, 4,000 RPM for 15s, idle for 15s, repeated 10 times) to try and induce a fault. If the codes set during this test, it confirms a failing oil pump.

Wiring & Ground Locations

• Engine Oil Pressure Sensor Connector — On the engine block, where the oil pressure sensor is installed. It is a 3-pin connector. On the 1.4L LUV engine, this is often on the back of the block near the oil filter housing and can be difficult to access.. The connector itself or the pigtail wiring can be damaged by heat and vibration, causing intermittent signals. Oil can also leak through a failed sensor and contaminate the terminals, causing a bad connection.
• G103 — Typically located at the left rear of the engine compartment on the cowl, above the brake booster on many GM platforms.. This is a major ground point for the Body Control Module (BCM) and the Data Link Connector (DLC). While not a direct ground for the sensor itself, a poor connection at G103 can cause a wide range of communication and data processing errors within the vehicle's modules, potentially contributing to how the ECM interprets sensor data.

Real Owner Repair Stories

• Reddit user in r/ChevyTrucks (General GM Truck (illustrates a common platform-wide issue)) — Persistent P0521 code.
  ❌ Tried (didn't work) Replacing the oil pressure sensor with an aftermarket part.
  ✅ What actually fixed it Replacing the aftermarket sensor with a genuine OEM sensor resolved the code, suggesting the ECM is sensitive to the specific calibration of the original equipment part.
• Reddit user in r/ChevyTrucks (Chevrolet Truck) — Recurring P0521 code.
  ❌ Tried (didn't work) Replacing the oil pressure sensor.
  ✅ What actually fixed it The user reported that switching to a Mobil 1 M1-113A oil filter and ensuring proper oil levels resolved the issue, highlighting the engine's sensitivity to filter quality.

OEM Part Supersession History

• 12596951, 12621234 → 12673134 — Standard part evolution for improved reliability or manufacturing changes.
  Heads up: While aftermarket sensors exist, forum and TSB evidence suggests GM ECMs can be sensitive to non-OEM sensor calibrations, sometimes causing the P0521 code to persist even with a new, functional aftermarket part. Using the genuine GM/ACDelco part is the safest option.

Model Year Variations Within This Range

• 2017-2020: Starting with the 2017 facelift, an optional, higher-output 1.4L Turbo engine (RPO: LE2) with direct injection became available, producing 153 hp. The base engine remained the port-injected 1.4L LUV (138 hp). While the P0521 code applies to both, part numbers for some components and specific diagnostic details could differ slightly, though the primary causes (sensor, oil, filter, PCV) are common to both.

Diagnostic Flowchart

Used vs. New Parts: Buying Guide for This Vehicle

When a used part is the smart pick: For this repair, using used parts is generally not recommended. The primary failure components are low-cost wear items (sensor, filter screen) that should always be replaced new. A used valve cover could be considered if the cause is a failed PCV diaphragm and a new assembly is cost-prohibitive, but it carries the risk of the used part's PCV failing soon after.

Donor-vehicle mileage cap: roughly under 60000 miles for the part to have meaningful remaining life.

What to inspect on the donor part:

• For a valve cover: Inspect the part for any cracks or signs of extreme heat damage.
• Ask for the donor vehicle's mileage; lower is always better.
• Avoid parts from engines that show heavy sludge buildup when looking into the oil fill hole, as this indicates poor maintenance.

OEM-only on this vehicle (don't cheap out):

• Engine Oil Pressure Sensor: Many owner accounts and mechanic experiences indicate that the GM ECM is very sensitive to the voltage range of the sensor. Aftermarket sensors, even if they fit, can fail to resolve the P0521 code. Using a genuine ACDelco/GM sensor (PN 12673134) is strongly advised to avoid repeat work.
• Engine Oil Filter: These engines are sensitive to oil flow and pressure. Using a filter that meets GM's dexos specification, like the OEM ACDelco PF64, is critical. Low-quality aftermarket filters can cause pressure deviations.

Aftermarket brands forum-validated for this vehicle:

• For the oil filter, a Mobil 1 (e.g., M1-113A) is often cited by owners as a high-quality alternative to OEM that solved their P0521 issues.

Brands owners have reported issues with on this vehicle:

• Generic, unbranded, or 'white-box' oil pressure sensors and oil filters are frequently implicated in unresolved P0521 cases on GM vehicles.

Real Owner Stories

Aggregated from forums and TSBs cited above. Mileages and costs reflect what owners reported in those sources.

Related OBD-II Codes

• P0171 — This code (System Too Lean) often appears due to the same root cause as P0521 on the 1.4L Ecotec. A common failure of the PCV valve in the valve cover creates a vacuum leak, triggering P0171, and also causes excessive oil consumption, which can lead to a low oil level and trigger P0521.
• P06DD — This code for 'Engine Oil Pressure Control Solenoid Valve Stuck Off' is directly related. GM TSB PIP5152D discusses diagnosing P0521 alongside P06DD, as both can point to issues with the oil pump or its control system.
• P06DE — Similar to P06DD, this code for 'Engine Oil Pressure Control Solenoid Valve Stuck On' is mentioned in GM TSB PIP5152D as being related to P0521. It indicates a fault in the same oil pressure regulation system, often traced back to the oil pump.
• P0300 — A Random Misfire code can be a consequence of the underlying cause of P0521. If the actual oil pressure is critically low (due to a failing oil pump or clogged pickup tube), it can cause engine components to function improperly, leading to a rough-running engine and setting misfire codes.

Frequently Asked Questions