Fix P0523: Mechanic’s solutions that WORKED

The code P0523: Oil Pressure Sensor Voltage Too High indicates a fault in the vehicle’s oil pressure sensor circuit., which could lead to incorrect readings of the engine’s oil pressure. It’s essential to address this issue promptly as it can affect the engine’s lubrication and overall health.

P0523 quick overview

Meaning	P0523: Oil Pressure Sensor Voltage Too High
Is it serious?	Yes, it can be serious as it affects engine lubrication, potentially leading to engine damage.
Possible causes	– Faulty oil pressure sensor – Wiring issues in the sensor circuit – Corroded or damaged connectors – Problems with the engine control module (ECM) or powertrain control module (PCM) – Mechanical issues affecting oil pressure
How to diagnose?	Check Oil Level: Ensure correct oil level and condition. Inspect Sensor and Wiring: Look for damage or corrosion in sensor connectors and wiring. Voltage Measurement: Use a voltmeter to check sensor voltage. Scan for Additional Codes: Check for other related diagnostic trouble codes. Consult Technical Service Bulletins (TSBs): Check for any manufacturer-specific guidance. Evaluate ECM/PCM: Consider potential ECM or PCM issues, especially if other codes are present.

In simple terms, the P0523 code means that the car’s computer has detected that the voltage signal from the oil pressure sensor is too high. This could mean that the sensor is faulty, or there could be an issue with the wiring connected to it. It’s important to address this because the oil pressure sensor plays a critical role in monitoring the health of your engine.

How to fix P0523 – learn from mechanics

I looked into P0523 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 CTS, 3.6L

Issue + Repair History:

• Came in running rough with codes P0206, P0306, P0523, PO521, and PO443
• New A/C Delco plugs installed (replaced previous Autolite plugs)
• After replacing plugs, codes P0306 and P0443 remained
• Battery disconnected and reconnected, resulting in codes P0443 and P0523 returning with poor car performance

Other OBD2 Codes + Test Results:

• P0206: Injector circuit problem
• P0306: Misfire #6
• P0443: Evap purge control circuit fault
• P0521: Engine oil pressure sensor performance
• P0523: Engine oil pressure sensor circuit signal low

Suggestions to Fix Issue:

• Check oil level as low oil can affect cam VVT, leading to misfires
• Pay attention to the oil pressure issue; poor maintenance can lead to cam timing issues and misfires

Final Fix:

• Found engine oil 2 quarts low and black
• Replaced engine oil pressure sensor and changed oil
• After these fixes, the car ran well

Case #2: Chevrolet

Vehicle Information: 2013 Chevrolet Silverado 1500 LT, 5.3L

Issue + Repair History:

• Initially came in with gauge reading 0 but no noise in the engine.
• Oil pressure tested: around 40 psi.
• Sender and screen replaced; cold start pressure went to 60 psi and dropped to 40 psi at idle.
• Vehicle returned with gauge reading 0 again; data for sending unit read 129.9 psi.
• Oil pressure re-checked: around 40 psi at idle.
• Wiring from sender to computer checked and found okay.
• Replaced connector with a pigtail assembly and a new sensor due to oil in sensor socket.

Other OBD2 Codes + Test Results:

• P0521: Engine Oil Pressure Sensor Performance
• P0523: Engine Oil Pressure Circuit High Voltage
• Oil pressure at idle: 40 psi

Suggestions to Fix Issue:

• Flushing oil out to clear any debris.
• Checking for blocked oil passages.
• Ensuring correct oil level and quality.
• Checking for oil ingress in sensor socket.
• Testing sender unit with air pressure to verify gauge movement.
• Considering PCM-related issues.
• Replacing the oil pressure sensor.

Final Fix:

• Replaced connector with a pigtail assembly and a new sensor due to oil in sensor socket.
• Oil pressure returned to normal on the gauge after these fixes.

Case #3: Honda

Vehicle Information

• 2009 Honda Accord EX-L 3.5L
• Issue: MIL Lamp on
• Code: P0523 (Rocker Arm Oil Pressure Sensor High Voltage)

Issue + Repair History

• P0523 caused by corrosion in plug at oil pressure switch near oil filter housing.
• Honda does not offer a replacement plug, only the whole wiring harness.
• Temporary repair: Cleaned and pinched terminal for short-term connection.

Other OBD2 Codes + Test Results

• Not mentioned.

Suggestions to Fix Issue

• Use a pigtail from Partsgeek.com (Inter motor part #S-2325) for a 2017 Honda Accord 4 cylinder.
• Find a compatible connector from a junkyard, possibly from newer models (2006 & up Ridgeline, 2008 & up Accord or Fit).
• Remove damaged pin and install a new one.
• Purchase from FINDPIGTAILS.COM for a quick but pricey solution.
• Search for the sensor online to find compatible vehicles for the same plug.

Final Fix

• Temporary repair by cleaning and adjusting the terminal.
• Ordered a pigtail online (Part #S-2325) for future repair.

Case #4: Mazda

Vehicle Information

• 2018 Mazda CX-5 Grand Touring 2.5L
• Issues: No Start, Poor Idle Quality, Stall, MIL Lamp on

Issue + Repair History

• Car brought in for burning oil smell; dealership diagnosed cracked head.
• Confirmed oil leak between cylinders 2/3.
• Replaced complete head kit from Mazda.
• Experienced crank, no start condition with occasional pop.
• Codes reported: P0087 (Fuel Rail/System Pressure Too Low), P0171 (System Lean), P0101 (MAF), P0523 (Oil Pressure Sensor Circuit).
• Issue with injector installation; replaced seals.
• Zero compression on cylinders 1/4, 180 lbs on 2/3.
• Oil pressure test showed 30psi cranking at 300rpm.
• Oil Pressure/Temp Sensor to PCM found an open signal circuit; repaired.

Other OBD2 Codes + Test Results

• Not applicable.

Suggestions to Fix Issue

• Double-check all connectors for possible mix-up.
• Follow wiring diagrams to identify correct wires and sensors.
• Consider a short-term subscription to Mazda ESI for accurate wiring diagrams.
• Check for vacuum leaks and improper gasket placement.

Final Fix

• Repaired Oil Pressure/Temp Sensor circuit; improved oil pressure and engine performance off idle.
• Found valve cover gasket leak; repaired to fix lean condition.
• Discovered exhaust valve lifter issue in cylinder 1; corrected lifter placement.
• After addressing these issues, the vehicle started and ran well.

Case #5: Dodge

Vehicle Information

• 2001 Dodge Ram 2500 5.9L
• Issues: Surge, Cuts Out

Issue + Repair History

• Vehicle would lose power as if running out of fuel, then recover.
• Fuel filter and injection pump replaced; fuel pressure remained stable during incidents.
• Previously replaced oil pressure switch; code resolved.
• Lift pump also replaced.

Suggestions to Fix Issue

• Possible issues with oil pressure signal circuit; consider checking for shorts.
• Monitor Throttle Position Sensor (TPS) and fuel pressure at high pressure pump inlet.
• Look into possible problems with the Electric Fuel Lift Pump.
• Consider potential crank sensor or 5-volt feed circuit issues.
• Possibility of PCM (Powertrain Control Module) failure.

Final Fix

• Replaced the injection pump itself, despite no specific codes indicating it as the problem.
• Decision informed by pump builder’s recent training and expertise.
• After replacement, the customer reported the vehicle running fine.

Advice	Brief Description of Diagnostic Step
Check Power and Grounds	Verify the integrity of power supply and ground connections for related components and sensors.
Inspect Sensor Connectors	Examine connectors of sensors like MAP, APPS, and oil pressure sensors for corrosion, damage, or loose fit.
Monitor Sensor Voltage	Use a voltmeter to check for appropriate voltage levels at sensors like the APPS and ECT.
Consider ECM/PCM Issues	Evaluate the ECM/PCM for potential failure, especially if multiple sensor-related codes are present.
Review Related Sensor Functioning	Assess functioning of related sensors like TPS, fuel pressure sensors, and oil pressure sensors.
Clean and Replace Connectors	Clean corroded connectors and replace if necessary, particularly when corrosion is evident.
Analyze Fuel System Integrity	Examine the fuel system, including lift pump and injection pump, especially in cases of engine performance issues.