What does it mean?
The vehicle’s main computer, called the Powertrain Control Module (PCM), controls many of the vehicle’s sensors, controls, and electronic components. One sensor, called the oil pressure sensor or sender, detects the amount of (mechanical) oil pressure in the engine and transmits it as a voltage reading/value to the PCM. In some vehicles, this oil pressure value is then relayed to a gauge in the instrument cluster to show the driver the oil pressure; other times this gauge is not present, but there will be a warning light if there is a problem.
This specific engine code P0523 is triggered when the PCM sees a value that is too high in the engine oil pressure sender/sensor. The oil pressure sensor operates on a 5-volt circuit. Typically, this engine code will be triggered when the voltage is 4.6 or higher. With this fault code, the cause can be mechanical or electrical but is likely related to electricity. This code is related to these other oil pressure DTCs: P0520, P0521, P0522, and P0524.
Symptoms
Symptoms of a DTC P0523 can include:
High oil pressure gauge
Oil pressure warning light illuminated
Causes
Potential causes of a P0523 code include:
High oil pressure (mechanical oil pump failure)
High pressure due to a blockage/restriction in the oil passage(s)
Poor engine oil used
Faulty wiring or connection/connector in the oil pressure sender circuit
Faulty oil pressure sender/sensor
Diagnostic and Repair Steps
It’s a good idea to check for Technical Service Bulletins (TSBs) that may apply to your vehicle before going too far into diagnostics.
As a vehicle owner/DIYer, the first obvious thing to do is to check the oil level using the dipstick. You want to make sure the engine has the correct type and weight of oil and that it is not too old and thick or clogged.
Next, visually inspect the wiring and connectors of the oil pressure sending unit. Look for broken or frayed wires, burnt spots, loose or exposed cables, etc. Refer to a model-specific resource for the sender’s location.
A technician may start by performing a mechanical oil pressure test using a mechanical gauge and compare this reading with the sensor value as read by the PCM. They would use an advanced scan tool to do this. If the sensor or wiring is faulty, the mechanical gauge test will give the mechanic or technician an immediate sign of this. If you are DIYing this job, this is the next step as well.
Now, if you have ruled out that there is an actual problem with the oil pressure, the issue lies either with the sensor or the wiring/connectors.
Use a digital volt ohmmeter (DVOM) to check the sensor itself, and if it does not meet the manufacturer’s specifications, you should replace it. Also check the voltage going to the oil pressure sensor, ensuring it is getting 5 volts. Replacing the sensor/sender or fixing wiring issues will be the most likely repair for this code. If it checks out fine, test the wiring and connectors from the sensor to the PCM. Check that there is no break in the wiring due to chafing, pinching, etc. Ensure the electrical connectors are tight and free of corrosion.