Technical Description of OBD-II Trouble Code
The range/performance of the Engine Oil Pressure Sensor/Switch
This diagnostic trouble code (DTC) is a generic OBD-II powertrain code. It is considered generic because it applies to all makes and models of vehicles (1996-newer), although specific repair steps may vary depending on the model. In our experience, the P0521 engine code appears more often on Chevrolet, Dodge, GMC, Mercedes Benz, Pontiac, and Cadillac, but it applies to any make/model.
What does that mean?
The Powertrain Control Module (PCM), which is the vehicle’s main computer, controls many sensors, controls, and electronics in the vehicle. One of these sensors is the oil pressure sensor or sender, which detects the amount of mechanical oil pressure in the engine and relays that information as a voltage reading/value to the PCM. In some vehicles, this oil pressure value is then displayed on a gauge in the instrument cluster to show the driver the oil pressure. In other vehicles, there may be a warning light instead of a gauge.
This specific P0521 engine code is triggered when the PCM detects an unexpected value in the engine oil pressure sender/sensor. This value may be outside of its normal range or may be fixed when it should fluctuate. For this P0521 trouble code, the cause may be mechanical or electrical, but it is more likely to be electrical. This code is related to P0520, P0522, P0523, and P0524.
NOTE: This code is severe. If you have oil pressure issues with your engine, it could result in major damage. Get your vehicle checked ASAP.
Symptoms
Symptoms of a P0521 DTC may include:
Causes
Potential causes of a P0521 code include:
Diagnostic & Repair Steps
As mentioned earlier, this code should be addressed ASAP because if there is a mechanical problem like actual low oil pressure, it can be a major and expensive repair.
NOTE: For example, there are known service bulletins that apply to a number of certain 2005-2016 GM vehicles including Chevrolet, Cadillac, GMC, Pontiac, Buick, and Saab. The bulletin numbers are PIP4786C and PIP5276D. Check for any applicable TSBs for your vehicle, even if it’s not one of those, before proceeding with diagnostics.
As a vehicle owner / DIYer, the first obvious thing to do is to check the oil level using the dipstick. Make sure there is adequate oil in the engine and that the oil filter or drain plug are not leaking. It’s possible that you have low or no oil pressure because of a leak you are not aware of and the oil has been depleted. Alternatively, you may have recently had an oil change and the oil was not refilled or the filter was not tightened properly. There are various reasons why you may have a P0521.
If you did have the oil changed recently, verify that the correct oil is in the engine. The wrong oil can cause various engine codes.
Next, visually inspect the wiring and connectors at the oil pressure sending unit. Look for broken or frayed wires, burnt spots, loose or exposed wiring, etc. Refer to a model-specific resource for the location of the sender.
A professional technician would likely do two things: use a mechanical oil pressure tester installed on the engine to take an actual physical oil pressure check, and compare that reading with the values shown by the vehicle’s PCM. If you have access to an advanced scan tool and an oil pressure gauge, this may be an option for you as well.
Now, if you have ruled out that there is an actual problem with oil pressure, the problem lies either within the sensor or the wiring/connectors.
Use a digital volt ohm meter (DVOM) to check the sensor itself, and if it does not meet manufacturers specifications, you should replace it. Replacing the sensor/sender will most likely be the necessary repair for this code. If it checks out OK, test the wiring and connectors from the sensor to the PCM. Verify that there are no breaks in the wiring due to chafing, pinching, etc. Make sure the electrical connectors are tight and free of corrosion.
As you can see, there are a number of possible reasons for this code P0521. If you need help, stop by our forum.
