P0521 on 2020-2024 Buick Encore GX: Oil Pressure Sensor Causes and Fixes

What's Unique About the 2020-2024 Buick ENCORE GX

The 2020-2024 Buick Encore GX and its platform-mate, the Chevrolet Trailblazer, are subject to specific documented issues related to P0521. First, a widespread recall addresses an ECM software flaw where the module cannot clear a permanent P0521 code, even after the physical problem is fixed. Second, several Technical Service Bulletins (TSBs) link this code to other complex issues, including a faulty engine camshaft cover (PIP5947C), high resistance in the engine wiring harness (PIP5826B), and potential oil pump problems (PIP5932D).

Diagnostic Flowchart

Tap your situation to follow the diagnostic path that matches what you're seeing on this vehicle.

Symptoms You May Notice

• Check Engine Light is on
• Oil pressure warning light on the dashboard
• Oil pressure gauge reading abnormally high or low
• Rough idle or engine surge
• Engine misfire
• Blue smoke from the exhaust
• Excessive oil consumption

Most Likely Causes

1. Faulty Engine Oil Pressure Sensor 🔴 High Probability Sensors are common failure points due to constant exposure to heat and vibration. They can fail internally, sending erratic signals, or leak oil through the sensor body. Some GM vehicles also have a small filter screen under the sensor that can become clogged, leading to incorrect readings.
   How to confirm: After verifying actual oil pressure is correct with a mechanical gauge, test the sensor's output signal. If the signal is erratic, incorrect, or doesn't change with RPM, the sensor is faulty. Before replacing, inspect the wiring harness for damage as per TSB PIP5826B.
   Typical fix: Replace the engine oil pressure sensor and the small filter screen beneath it.
   Est. part cost: $25-$75
2. ECM Software Glitch (Permanent DTC) 🔴 High Probability A known issue covered by Voluntary Emission Recall #A222379710 / #A222379711. The ECM in certain 2020-2023 Encore GX and 2021-2023 Trailblazer models may not clear the permanent status of DTC P0521 after a repair, which can cause a failed emissions test.
   How to confirm: If the P0521 code returns immediately after replacing the sensor and clearing codes, and the vehicle's VIN is part of the recall, this is the likely cause. A GM dealer can verify VIN eligibility.
   Typical fix: The dealer must reprogram the Engine Control Module (ECM) with updated software. This is performed at no charge if the vehicle is covered by the recall.
   Est. part cost: $0 (if covered by recall)
3. Low or Incorrect Engine Oil 🟡 Medium Probability This is a universal cause for any vehicle. Using oil of the wrong viscosity (e.g., not DEXOS-approved for this engine) or having a low oil level can cause pressure readings outside the normal range.
   How to confirm: Check the engine oil level on the dipstick and verify its condition. Ensure the correct oil type (as specified in the owner's manual) is being used.
   Typical fix: Perform an oil and filter change with the manufacturer-specified oil. 🎬 Watch: Buick Encore GX oil change and maintenance light reset.
   Est. part cost: $40-$80
4. Engine Camshaft Cover Issue ⚪ Low Probability TSB #PIP5947C specifically identifies an internal failure of the camshaft cover on some 2024 models that can lead to P0521, excessive oil consumption, and other codes, particularly at very low mileage (<2,000 miles).
   How to confirm: This requires in-depth diagnosis, often prompted by symptoms like blue exhaust smoke and oil fouling on all spark plugs. A technician will follow the diagnostic procedure in the TSB.
   Typical fix: Inspection and replacement of the engine camshaft cover.
   Est. part cost: $150-$300

Rare But Worth Checking

• Wiring Harness Damage: TSB #PIP5826B details a potential for high resistance in the engine wiring harness, specifically a faulty splice, causing P0521 on 2020-2021 models. The TSB provides a procedure for manipulating the harness while monitoring the oil pressure reading on a scan tool to confirm.
• Failing Oil Pump or Worn Engine Components: This is the worst-case scenario. TSB #PIP5932D mentions diagnostic testing for the oil pump in relation to P0521. If a mechanical gauge confirms that the actual oil pressure is low, it points to a serious internal engine problem like a bad oil pump (potentially a stuck relief valve), clogged oil passages, or worn bearings.

Diagnosis Steps

1. Check the engine oil level and condition. Top off or change if necessary, using the manufacturer-specified oil.
2. Connect an OBD-II scanner to confirm the P0521 code and check for any other stored codes.
3. Check for open recalls using the vehicle's VIN, specifically #A222379711, related to the permanent DTC issue.
4. Inspect the oil pressure sensor's electrical connector and wiring for any signs of damage, oil saturation, or corrosion.
5. Following the procedure in TSB #PIP5826B, manipulate the engine wiring harness near the underhood fuse block while monitoring oil pressure data to check for high resistance.
6. Connect a mechanical oil pressure gauge to the engine to verify the actual oil pressure. Compare the reading to the manufacturer's specifications (e.g., TSB #PIP5826B specifies 23-29 psi at idle and 49-55 psi at 4000 RPM when hot).
7. If actual oil pressure is good, the sensor or its filter screen is the primary suspect. Replace the engine oil pressure sensor and the screen underneath it.
8. If actual oil pressure is low, further mechanical diagnosis is needed per TSB #PIP5932D to check for a failing oil pump, clogged oil passages, or worn engine components.
9. If the code persists after replacing the sensor and verifying good pressure, the vehicle likely needs the ECM reprogrammed by a GM dealer per recall #A222379711.
10. If symptoms include heavy oil consumption and smoke on a low-mileage 2024 model, investigate the camshaft cover per TSB #PIP5947C.

Parts You'll Likely Need

• Engine Oil Pressure Sensor (OEM #12673419 (also known as ACDelco D1846A)) — This sensor is the most common component to fail, sending incorrect readings to the ECM. Using an OEM part is often recommended to avoid persistent issues.
  Trusted brands: ACDelco, GM Genuine
  OEM price range: $40-$75
  Aftermarket price range: $25-$50
• Engine Oil Pressure Sensor Filter Screen — This small screen sits below the sensor and can become clogged with sludge, restricting oil flow to the sensor and causing a false low-pressure reading. It is often replaced with the sensor.
  Trusted brands: Dorman, GM Genuine
  OEM price range: $5-$15
  Aftermarket price range: $3-$10

Related Codes That Often Appear With This One

• P0300 — TSB #PIP5947C links P0521 with a random misfire code (P0300) due to the camshaft cover issue causing oil-fouled spark plugs.
• P050D — Associated with cold start rough idle, also mentioned in TSB #PIP5947C.
• P06DE — Indicates Engine Oil Pressure Control Solenoid Valve Stuck On. This code is often seen with P0521 as they are part of the same system. It is also cited in TSB #PIP5947C.
• P1101 — Indicates an intake air flow system performance issue, which can be triggered by the camshaft cover problem described in TSB #PIP5947C.

Technical Service Bulletins (TSBs) & Recalls

• PIP5947C: Addresses a potential camshaft cover issue on 2024 models that can cause P0521 along with misfires and exhaust smoke.
• A222379710 / A222379711: Recall concerning the ECM's inability to clear the permanent status of DTC P0521 on 2020-2023 models, requiring a dealer software update.
• PIP5826B: Details diagnosis for high resistance in the engine wiring harness on 2020-2021 models.
• PIP5932D: Mentions diagnostic testing related to the oil pump for P0521.

Platform-Specific Known Issues

• ECM Permanent DTC Glitch: A Voluntary Emission Recall (#A222379710 / #A222379711) was issued because the ECM may not properly clear the permanent status of DTC P0521. This means even after a successful repair, the Check Engine Light may remain on until a dealer reprograms the ECM. This affects 2020-2023 Encore GX models.
• Camshaft Cover Complications: TSB #PIP5947C notes that P0521 can be set due to an internal failure of the engine camshaft cover on 2024 models, which may also cause symptoms like misfires (P0300) and blue exhaust smoke, especially in new vehicles with under 2,000 miles.
• Wiring Harness Resistance: TSB #PIP5826B points to high resistance in a specific splice within the engine wiring harness as a cause for P0521 on 2020-2021 models, requiring harness inspection and repair rather than sensor replacement.

Mechanic-Grade Diagnostic Values

• Engine Oil Pressure at Idle (Hot) — expected: 160 - 200 kPa (23.21 - 29.01 psi). Failure: Pressure significantly above or below this range indicates a mechanical issue or sensor error.
• Engine Oil Pressure at 4000 RPM (Hot) — expected: 340 - 380 kPa (49.31 - 55.11 psi). Failure: Pressure significantly above or below this range indicates a mechanical issue or sensor error.
• Engine Oil Pressure Sensor Signal Voltage — expected: Varies with pressure, typically 0.5V (low pressure) to 4.5V (high pressure).. Failure: Voltage is stuck, erratic, or does not correspond to mechanically-gauged pressure.

Scan Tool Commands That Help

• GDS2 (GM Dealer Scan Tool): Data Display > Engine Mechanical Data > Engine Oil Pressure (PSI) — This specific PID must be used for diagnosis per TSB #PIP5826B, as other PIDs like 'Engine Oil Pressure Sensor' are not usable for the harness wiggle test.
• GDS2 (GM Dealer Scan Tool): Engine Speed Control — Used to hold the engine at a specific RPM (e.g., 4000 RPM) to compare actual mechanical oil pressure with the scan tool data to verify sensor accuracy under load, as specified in TSB #PIP5826B.
• GDS2 (GM Dealer Scan Tool): Clear All DTCs — Required before performing specific diagnostic drive cycles, such as the one outlined in service update A202302140, to see if P0521 sets under specific test conditions.

Wiring & Ground Locations

• Special 3-wire Splice (Low Reference circuit 548 BK/GN) — Inside the main engine wiring harness, in the branch leading to the X50A Underhood Fuse Block.. TSB #PIP5826B identifies this specific splice as a point of high resistance that can directly cause P0521 on 2020-2021 models. The fix requires opening the harness to repair the splice, not replacing the sensor.
• 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). A poor connection here can cause a wide range of communication and sensor reading errors, including issues with the ECM processing the oil pressure sensor signal.
• Engine Oil Pressure Sensor Connector — On the engine block, where the oil pressure sensor is installed. It is a 3-pin connector.. The connector itself or its pigtail wiring can become damaged from heat and vibration, causing an intermittent or failed connection that triggers P0521.

Real Owner Repair Stories

• Reddit user in r/ChevyTrucks (General GM truck (not specific to Encore GX, but illustrates a common GM issue)) — Persistent P0521 code after replacing the sensor.
  ❌ Tried (didn't work) Replacing the oil pressure sensor with an aftermarket part from a local auto parts store.
  ✅ What actually fixed it Replacing the aftermarket sensor with an OEM sensor resolved the issue. This suggests that some GM engine computers are sensitive to the specific calibration of the original equipment sensor.

OEM Part Supersession History

• 12616646 → 12673419 (Current PN for ACDelco D1846A) — Standard part evolution for improved reliability or manufacturing process changes.
  Heads up: While multiple numbers exist (12573107, 12614969, 12616646), they all supersede to the current GM/ACDelco part. Using a non-OEM part has been reported by users to cause persistent codes, making it crucial to stick with GM or ACDelco branded sensors.

Model Year Variations Within This Range

• 2024: The 2024 model received a significant facelift with new interior tech and exterior styling, but the core 1.2L and 1.3L powertrains remained the same. However, TSB #PIP5947C specifically calls out 2024 models for a potential camshaft cover issue causing P0521 at very low mileage, a problem not highlighted for earlier years.
• 2020-2021: TSB #PIP5826B, which details the specific wiring harness splice issue, is explicitly for 2020-2021 Encore GX and 2021 Trailblazer models. This suggests the harness construction or routing may have been changed in later years.
• 2020-2023: The Voluntary Emission Recall (#A222379710 / #A222379711) for the permanent DTC glitch applies to models up to 2023, implying that 2024 and later models should have the corrected ECM software from the factory.