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P0521 Fault in 2012 GMC Sierra 1500: Oil Pressure Gauge Reads 0 Despite Actual Oil Pressure

Model: 2012 GMC Sierra Fault Code: P0521 Posted: 2018-03-05 08:41

Hello everyone, I'm seeking advice on a persistent issue with my 2012 GMC Sierra 1500 5.3L V8. Last week, the vehicle triggered Diagnostic Trouble Code (DTC) P0521 — indicating an oil pressure sensor circuit malfunction. On Friday morning, when I started the truck, the oil pressure gauge read exactly zero, even though I could hear and feel normal engine operation. The engine runs smoothly with no rough idle or performance issues. I recently performed a standard oil change, which did not resolve the issue. I also inspected and replaced both the oil pressure sensor and its associated screen, as they were found to be dirty. All wiring connections near the harness appear intact — no damage, rubbing, burns, or fraying. The engine itself seems fully functional with normal oil pressure (verified by manual feel), yet the gauge remains at zero. I'm now wondering if this points to a faulty instrument cluster, a defective potentiometer circuit, or an issue in the sensor signal wiring. I don't have a scan tool with bi-directional control, so I can't perform live signal testing. Any suggestions on next steps would be greatly appreciated — especially regarding how to verify the sensor signal or test the gauge unit directly? Thanks for any insights or troubleshooting tips!

Related fault codes
P0521
Comments (5)
Anonymous 2018-03-06 07:41

Try jumping the grey wire and tan/white wire at the oil pressure sender to see if the gauge responds with a reading during engine cranking (koeo). If no response, check for 5V power on the grey wire when the engine is off. A good signal suggests an open circuit in the sensor wiring or a faulty gauge unit. Do you have access to a scan tool with bi-directional controls? That would help verify live signals.

Anonymous 2018-03-06 07:47

Initial thought: Check the valve lifter oil filter (part #452 in service diagrams) and consider adding a bottle of 'Risolone' — an oil detergent — to improve circulation. The oil pressure sensor is located at part #706, so ensure it's properly seated and not clogged.

Anonymous 2018-03-06 08:51

Thanks for the guidance! I'll test the sensor resistance this afternoon and update with my findings — fingers crossed it’s not a faulty unit or wiring issue.

Anonymous 2018-03-06 09:03

It's unlikely to be the oil pressure sensor itself, especially since it has already been replaced. Unless the filter was severely clogged during removal, engine gumming is improbable. Over time, screen buildup typically causes a gradual drop in oil pressure — if this issue appeared suddenly, it’s more likely related to the potentiometer circuit or gauge assembly. Given that the sensor was replaced and the gauge still reads zero, the problem may lie in the instrument cluster or signal wiring.

Anonymous 2018-03-07 08:58

Thanks for all the helpful input — really appreciated! Long story short: The replacement oil pressure switch I installed was defective. After replacing it with a known-good unit, everything is now working correctly. Thanks again for your support!