Fix P0521: Mechanic’s solutions that WORKED

The P0521: Engine Oil Pressure Sensor/Switch Range/Performance code indicates an issue with the engine’s oil pressure sensor or switch, particularly relating to its performance or the range of readings it provides. If the sensor detects readings outside the normal range or performs erratically, it triggers this fault code.

P0521 quick overview

Description	P0521: Engine Oil Pressure Sensor/Switch Range/Performance
Is it serious?	This code can be serious as it relates to engine oil pressure, which is crucial for engine health and performance.
Possible causes	– Faulty oil pressure sensor or switch – Low engine oil level or poor oil quality – Blocked oil passages in the engine – Faulty oil pump or damaged components – Wiring or electrical issues related to the oil pressure sensor – Worn or damaged engine components affecting oil pressure
How to diagnose?	Check Oil Level and Quality: Ensure the engine oil level is adequate and the oil is in good condition. Inspect Oil Pressure Sensor: Examine the oil pressure sensor for damage or faults. Evaluate Wiring and Connections: Look for damaged wiring or poor connections related to the sensor. Manual Oil Pressure Test: Use a manual gauge to test the actual oil pressure. Check Oil Pump and Passages: Inspect the oil pump and internal oil passages for blockages or damage. Scan for Additional Codes: Use a diagnostic scanner to check for other related engine codes. Monitor Engine Performance: Observe the engine’s performance and noises for indications of internal problems.

How to fix P0521 – learn from mechanics

I looked into P0521 service cases at iatn.com website where in the private forums the mechanics seek advice from other mechanics. I looked up a bunch of cases to help you decide how to fix your issue and see what would a real mechanic do to solve it.

Case #1: Cadillac

Vehicle Information: 2005 Cadillac STS 4.6L – MIL Lamp on

Issue + Repair History:

• The vehicle runs fine without any warning bells.
• The only issue is the Check Engine Light (CEL) being on.
• Visual inspection didn’t reveal anything unusual.
• Seeking diagnostic charts for the car, as information from Mitchell was insufficient.

Other OBD2 Codes + Test Results:

• P0522: Oil pressure circuit low voltage
• P0521: Engine oil pressure sensor range/performance

Suggestions to Fix Issue:

• Check oil sending unit for loose connection; if not, consider replacing it.
• Investigate if these Diagnostic Trouble Codes (DTCs) typically illuminate the CEL.
• Review the diagnostic procedure for DTC P0521 and P0522, especially regarding the Engine Oil Pressure (EOP) sensor’s performance and circuit voltage.
• Ensure other potential issues aren’t causing the CEL to activate.
• Check the wiring schematic for the circuit if available.

Final Fix: The problem was resolved by replacing the oil pressure sensor. The technician was not entirely confident that this was the initial issue, but it did cure the problem for the time being. No other codes were stored, and the CEL activation cause was uncertain.

Case #2: Chevrolet

Vehicle Information: 2009 Chevrolet Silverado 1500 LT 5.3L – MIL Lamp on

Issue + Repair History:

• Check engine light on with a P0521 code.
• Initially replaced the oil pressure sensor, but the light returned a few days later.
• Technician believes there is no actual engine oil pressure issue.

Suggestions to Fix Issue:

• Check pigtail at switch for problems.
• Confirm good oil pressure before proceeding further.
• Verify if Active Fuel Management is switching properly.
• Investigate the filter under the oil pressure switch.
• Manually check oil pressure to ensure it’s not an actual issue.
• Inspect the filter screen in front of the oil pressure sensor for clogging.
• Check oil level, considering these engines tend to consume oil.
• Examine the possibility of a restricted screen/filter under the oil pressure sensor or a cam bearing issue in the block.
• Look into the o-ring on the oil pickup tube, especially if the gauge shows low at idle after warming up.
• Replace the oil filter for the valve lifter oil manifold if clogged.

Final Fix: The issue was resolved by replacing the oil pressure “screen” located below the oil pressure sensor. It’s recommended to replace this screen whenever the sensor is replaced, even if it appears to be in good condition. The technician confirmed this as the fix after ensuring the problem did not reoccur.

Case #3: Buick

Vehicle Information: 2006 Buick LaCrosse CXS 3.6L – All Gauges Not Working

Issue + Repair History:

• After receiving a new battery and cable end, all gauges stopped working (speedometer, gas, temperature, tachometer), and the traction control light turned on.
• Code U1000 stored in the instrument cluster; full system scan revealed U1300, P0521 (oil pressure sensor performance), and P1629 (theft deterrent fuel enable signal not received).
• Possible causes considered include a bad Electronic Control Unit (ECU).

Suggestions to Fix Issue:

• Check all fuses thoroughly.
• Disconnect battery cables, connect them together for 15 minutes, then reconnect to reset the system.
• Confirm no backward jump start occurred, as it can cause significant damage.
• Investigate problems on the Class 2 network; if any module sends bad data or is grounded, it can disrupt communication.
• Communicate with individual modules to identify the issue.
• Consider disconnecting modules one at a time to see if it revives the data lines.
• Try a key relearn procedure by leaving the key in the “on” position for extended periods and resetting the ignition.
• Replace and reprogram the ECU if necessary, as it might have been damaged due to a reverse jump or battery connection issues.

Final Fix: The issue was resolved by concluding that the ECU was bad. The vehicle was sent to the dealer for repair, where replacing and flashing the computer fixed the issues.

Case #4: Chevrolet

Vehicle Information: 2012 Chevrolet Silverado 1500 LT 5.3L – Oil Pump, CYL2 Misfire

Issue + Repair History:

• After installing a new oil pump, sensor, and screen, the truck runs perfectly except for a misfire at idle only on cylinder 2.
• The Active Fuel Management (AFM) is inhibited due to the oil pressure sensor.
• Error codes include P0300 and P0521.
• Oil pressure measured at 6 psi at idle at the pressure sensor and 10 psi at the filter housing.
• The truck was taken by the customer for a drive, with a plan to recheck oil pressure upon return.

Suggestions to Fix Issue:

• Perform a running compression test on cylinder 2 and check for pitting on the camshaft.
• Confirm that the oil pressure is not too low, possibly indicating a bad relief valve in the oil pan.
• Check compression first, considering potential lifter issues on cylinder 2.
• Inspect for bad cam bearings if oil pressure is confirmed low with a manual gauge.
• Disconnect all injectors and run the vehicle on an alternative fuel source to check if misfire persists.
• Consider crank end play issues that might cause oil pressure and misfire issues.
• Use a specific Delco oil filter (PF48E) and check the pickup screen in the VLOM for debris.
• Check for worn cam or lifter roller on cylinder 2 through static and running compression tests.

Final Fix: The customer drove the truck for a couple of weeks with no oil pressure issues but still experienced misfires at idle. The technician used resources from IATN and Mitchell for guidance. The specific resolution to the misfire issue was not detailed in the summary.

Case #5: Chevrolet

Vehicle Information: 2007 Chevrolet Tahoe LTZ 5.3L – AFM Lifters Issue

Issue + Repair History:

• The vehicle came in with codes P0300 and P0521, and a valve train noise isolated to the passenger side.
• Discovered a collapsed AFM lifter on cylinder 6.
• Replaced all 8 AFM lifters, head gaskets, and cylinder head bolts. Surfaced cylinder heads and did a valve job.
• After reassembly, experienced active misfires primarily on cylinder 6, and a few on 5, then later on cylinders 4 & 1.
• Replaced spark plugs on #5 & 6, ignition coil on #6, swapped fuel injectors, and replaced the solenoid valve assembly.
• Service Stabilitrak/Traction Control warnings and a flashing check engine light (code P0300) appeared.
• Oil pressure at idle was 19psi and near 50 psi at 3000 rpm.

Suggestions to Fix Issue:

• Measure actual cam lobe lift and compare to others.
• Perform a crank relearn procedure.
• Check for camshaft wear and roller pitting on the old lifters.
• Drop the oil pan and pickup, clean, and replace O-rings for potential oil starvation issues.
• Inspect the cam lobes for pitting when replacing AFM lifters.
• Check compression on the affected cylinders and verify correct oil pressure.
• Suspect a camshaft or oil pump failure if oil pressure is low.
• Consider the possibility of a worn cam affecting lift and causing misfires at idle.

Final Fix:

• The engine was disassembled again after failing an AFM compression test.
• Found 3 AFM lifters had become “unlocked”, leading to oil pressure bleeding off.
• Replaced all the AFM lifters and reassembled the engine, as the camshaft showed normal wear.
• This resolved the issue, highlighting the importance of checking for lifter locking even when they are newly replaced.

Common Advice for P0521 Code	Brief Description of Diagnostic Step
Check Oil Pressure	Verify oil pressure with a manual gauge to confirm if it’s within the specified range.
Inspect Camshaft and Lifters	Look for wear, pitting, or damage on the camshaft and lifters, especially AFM lifters in GM vehicles.
Perform Crank Relearn Procedure	Conduct a crankshaft position relearn to ensure proper timing and engine performance.
Examine Oil Pump and Pickup Tube	Investigate the oil pump functionality and condition of the pickup tube, including O-ring replacement.
Assess Valve Train Components	Check for issues in the valve train, such as lifter collapse or improper installation.
Analyze Engine Compression	Perform a compression test to identify any cylinder-specific issues that may contribute to the fault code.
Inspect Electrical Connections	Ensure all related electrical connections, including sensors and wiring, are secure and undamaged.