P0523 is a standard OBD2 trouble code that can occur in the GMC Sierra. In layman’s terms, it indicates the signal from the oil pressure sensor is higher than its normal operating range (in terms of voltage).
P0523 is generic (it has the same definition for all vehicles), repair steps will depend on your Sierra’s model year and the engine equipped.
A bad oil pressure sensor is the most common cause of P0523. However, an oil system issue could trigger this code as well. Don’t assume the sensor is bad until you confirm the oil pressure manually. If there’s an oiling issue, it can cause engine damage or failure.
P0523 Definition: Engine Oil Pressure Sensor/Switch – High Input
Here’s precisely what P0523 is telling you:
Oil Pressure Sensor/Switch
The oil pressure sensor bolts into your Sierra’s engine and relays the oil pressure reading to the Powertrain Control Module (PCM). It converts the mechanical pressure reading into a voltage value that the PCM understands.
From the PCM, the oil pressure is sent to the oil pressure gauge (or warning light).
High Input
The voltage value is almost at or above its highest possible value (which tells the PCM that the oil pressure level is very high). If the input was low, you’d have P0522.
GMC Sierra P0523 Symptoms
Your Sierra may feel like it’s running and driving fine, but even without symptoms, you shouldn’t drive it with P0523 until you verify the oil pressure is fine.
Here are the most common symptoms associated with P0523:
- Check engine light
- High oil pressure reading on the gauge or the oil pressure light could be on
P0523 GMC Sierra Causes
Two things are going on. Either the oil pressure is too high, or there is an issue related to the oil pressure sensor.
Here are the most common causes of P0523 in the GMC Sierra and the proper order to check them.
Check the Oil
Verify that the oil level isn’t overly full. Is it sludgy? Is it the proper weight? If you didn’t pour it in yourself, it’s possible that the wrong viscosity was used the last time the oil was changed. Consider this possibility if you got P0523 right after an oil change.
Bad Oil Pressure Sensor – Wiring
If the oil level is correct, it’s not old, and it’s the proper viscosity, it’s time to look at your Sierra’s oil pressure sensor. A wiring failure is widespread with these sensors due to their proximity to the exhaust.
Inspect the harness for any obvious damage. Look for cracked, broken, burnt, or brittle wiring. Follow the harness as long as you can, but pay particular attention to it within a couple of feet of where it plugs into the head.
Test the Oil Pressure Sensor
You can test the oil pressure switch/sensor with a simple multimeter. The video below will show you how to do it for just about every type of oil pressure sensor.
You could also get a mechanical oil pressure tester from a place like AutoZone or Harbor Freight. They’re usually around $25-$40 and will 100% tell you if you have a real oil pressure problem. That’s about the same price as a new oil pressure sensor, and you’ll be plugging into the same hole anyway.
If the manual oil pressure checks out, you have positive proof that your Sierra doesn’t have a sensor or wiring issue.
Mechanical Issues
While a bad oil pressure sensor or wiring issue is the most common cause of P0523, it’s not the only one. If your Sierra has a faulty oil pump or restricted oil passaged can also cause this code. You can verify this with an oil pressure test kit (it’s just a mechanical oil gauge with adapters to fit most makes/models).
Conclusion
While there are a few issues that can cause P0523 in they GMC Sierra, start by checking the oil and testing the oil pressure sensor. More often than not, that’ll fix the code. Good luck!