P0523 on the 6.6L Duramax L5P is an engine oil pressure sensor circuit high input fault. The oil pressure sensor reports pressure to the ECM, which uses it for the gauge, warnings, and protection strategy. P0523 sets when the sensor signal voltage reads too high, corresponding to an implausibly high pressure, which almost always indicates a circuit or sensor problem rather than real oil pressure.
Oil pressure monitoring exists to protect one of the most expensive parts of your truck, so any code touching it deserves a careful look even when the fault turns out to be electrical. On the L5P the sensor feeds both the driver display and the ECM protection strategy, which means a false high reading can mask a genuine low-pressure event later on. Confirming what the sensor is actually reporting, and why, is the key to closing out P0523 with confidence.
What P0523 means
The oil pressure sensor outputs a voltage proportional to pressure. P0523 means that voltage is at the high end of the scale beyond the plausible range, which typically points to a short to voltage in the signal wire, a failed sensor, or a connector problem. Because true oil pressure rarely spikes that high, the code is usually electrical.
Common causes
- Failed oil pressure sensor
- Signal wire shorted to a voltage source
- Corroded or damaged sensor connector
- Chafed harness contacting a power wire
- Loss of proper ground reference at the sensor
Symptoms
- Check engine light with P0523 stored
- Oil pressure gauge reading pinned high or erratic
- Possible warning messages in the driver display
- Usually no change in actual engine behavior
- Intermittent readings if the fault is a loose connection
How to diagnose it
Compare the scan tool oil pressure reading to the gauge; a value pinned unrealistically high confirms the electrical fault. Inspect the sensor connector for corrosion, spread pins, and a secure lock. Check the signal wire for a short to voltage and verify the ground and reference. If you can safely confirm actual oil pressure with a mechanical gauge, do so to prove the reading is false before replacing parts. A sensor that reads high with a good circuit is the likely culprit.
How to fix it
Repair a signal wire shorted to voltage and clean or replace a corroded connector, which resolves many P0523 cases. If the wiring is good but the sensor reads high, replace the oil pressure sensor. After the repair, clear the code and confirm the reading returns to a normal value at idle and under load. Because oil pressure protects the engine, do not ignore this code; confirm the reading is accurate after the fix. For an oil pressure sensor for your L5P Duramax, contact sales@coredieselparts.com.
Frequently asked questions
Is my oil pressure really high with P0523?
Almost never. P0523 usually means an electrical fault reading falsely high. Confirm with a mechanical gauge if you want certainty, but the sensor or wiring is the typical cause.
Can I drive with P0523?
You can usually drive short distances since the fault is electrical, but you lose accurate oil pressure monitoring. Repair it soon so you do not miss a real low-pressure event.
What is the difference between P0523 and P0522?
P0523 is the circuit reading high and P0522 is the circuit reading low. Both point to the oil pressure sensor circuit from opposite electrical directions.
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