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 diagnostic trouble code P0520 is triggered when the PCM sees a value from the engine oil pressure sender that is outside its normal range. For this P0520 fault code, the cause is likely electrical. This code is related to P0521, P0522, P0523, and P0524.
Symptoms
Symptoms of a DTC P0520 may include:
Malfunction Indicator Lamp (MIL) is illuminated (i.e., Check Engine light)
Oil pressure gauge reading low or high
Oil pressure warning light illuminated
Causes
Potential causes of a P0520 code include:
Faulty engine oil pressure sensor
Excessive resistance in the oil pressure sensor circuit
Short circuit in the circuit to/from the oil pressure sensor and/or the PCM and/or ground
Faulty PCM (less likely)
Diagnostic and Repair Steps
A good starting point is always to check the Technical Service Bulletins (TSBs) for your vehicle. Your issue may be a known problem with a known fix released by the manufacturer and can save you time and money when diagnosing.
Specifically, we know that for Dodge-Chrysler-Ram-Jeep models, it is bulletin #18-034-14.
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 there is enough oil in the engine and that the oil filter or drain plug is not leaking or something similar. It is possible that your oil pressure is low or zero because you have a leak you are unaware of and the oil is gone. Or, perhaps you just had an oil change and the place forgot to refill the oil, tighten the filter sufficiently; there are various reasons why you might have a P0520 or related codes.
Next, visually inspect the wiring and connectors of the oil pressure sending unit. Look for broken or frayed wires, burnt spots, loose or exposed wiring, etc. Ensure the electrical connections are tight and not oily or contaminated, etc. Refer to the model-specific repair manual for the sender’s location. *Remember, codes never indicate which parts to change, but where to start diagnosis*.
The next step, if nothing seems obvious, is to use a digital voltmeter (DVOM) to probe the terminals of the oil pressure sensor, both at the sensor itself and on the associated wiring and harness. Compare to factory specifications. Specifically check for short circuits to ground, resistance that is not within specifications (depends on your model/engine). Repair as necessary.
In all likelihood, the fix will be one of two things: a wiring issue that needs to be repaired or a sensor that needs to be replaced. Replacing the PCM is more of a last resort and should only be done after proper diagnosis.