Error Code P0523 is defined as Engine Oil Pressure Sensor/Switch High Voltage. This is a generic trouble code, meaning it applies to all vehicles equipped with OBD-II system, particularly those made since 1996 up to present. It is particularly common among Cadillac, Chevrolet, Dodge, GMC, Mercedes Benz, and Pontiac models. Specifications on the definition, troubleshooting, and repairs, of course, vary from one make and model to another.

The PCM (powertrain control module, also known as ECM or engine control module in other vehicle makes) is the vehicle’s computer system which controls multiple controls, electronics, and sensors. One of these sensors is the ‘Oil Pressure Sensor’ or ‘Oil Pressure Sender’ which detects the amount of (mechanical) oil pressure in the engine. It relays information through voltage reading value to the PCM. For some vehicles, oil pressure value is relayed to a gauge in the instrument cluster, showing the driver the oil pressure. Sometimes, however, there is no gauge; rather, there will be a warning light to notify the driver about the problem.

When Error Code P0523 is detected, that means the PCM has determined a too high of a value in the engine oil pressure sender/sensor. The sensor works as a 5V circuit, and generally, the code is triggered when the voltage is at 4.6V or higher. This problem could be mechanical or electrical, but in many cases, it points to the latter.

Other related error codes include:

Common Symptoms

As with other error codes, this code activates the Check Engine light and registers the code to the vehicle’s memory system. Other common symptoms include:

  • Too high reading in oil pressure gauge
  • Oil pressure indicator lamp activated

Possible Causes

  • High oil pressure (defective mechanical oil pump)
  • High pressure caused by obstruction/restriction in oil passage(s)
  • Use of wrong engine oil
  • Faulty connector or wiring in the oil pressure sender circuit
  • Defective oil pressure sender/sensor

How to Check

A good starting point in diagnosing this code is with the use of TSB (technical service bulletin) for the vehicle’s specific make and model.

Next is to check the level of oil using a dipstick. Also, you need to make sure the engine has the right type and weight of oil, and it’s not overdue for a change (not too old, thick, and sludged up).

Next, check the connectors and wirings at the oil pressure sending unit. Look for signs of damages such as burnt spots, frayed wires, loose or exposed wirings. To locate the sender, you can check with the specific resource.

In some cases, technicians will also put on a mechanical oil pressure gauge to verify the actual oil pressure and compare that to the sensor reading using an advanced scan tool. If the sensor or wirings are faulty, then the mechanical gauge test will provide an immediate sign of that.

If you have already ruled out the problem with oil pressure, then you could check if the problem results from issues in the sensor, connectors, or wirings.

Check the sensor using the DVOM. If it does not meet the specs set by the manufacturer, then it must be replaced.

Also, make sure you check the voltage that goes to the oil pressure sensor, it should be 5V.

Replacement of the sender/sensor or repairing wiring issues will be the most common repair for this code. If they’re in good condition, then test the wiring and connectors from the sensor to the PCM. Make sure there are no breaks in the wiring, chafing, or pinching. Also, make sure the electrical connectors are tight, and there is no corrosion.

How to Fix

  • Changing out the oil
  • Resetting the oil pressure sensor
  • Repair or replacement of faulty oil pressure sensor wirings and connectors
  • Replacement of oil pressure sensor

This code is a serious problem, as it points to a very important component of the engine – the oil system. The engine could have not enough oil or could be using the wrong type of oil. It can also be caused by a leak. Thus, this code must be addressed as soon as possible. Waiting too long could cause the engine to seize up and could result in more serious and expensive damages.