P0520 Engine Oil Pressure Sensor/Switch Circuit Malfunction
If you own a GM vehicle and have a trouble code P0520 Engine Oil Pressure Sensor/Switch Circuit Malfunction, start your diagnosis with the oil pressure switch. Ford uses an inertia shutoff switch to shut down the fuel pump if the vehicle is involved in an accident. GM uses the oil pressure switch as an inertia fuel shutoff.
When turning the key to the RUN position, PCM provides ground to the fuel pump relay for 2-seconds to power the pump and build pressure. Then, during cranking it provides voltage to the fuel pump. During cranking and RUN, the PCM also provides power to the oil pressure switch. As oil pressure builds during cranking, the oil pressure switch contacts close and complete the circuit to ground. So the PCM sees a large voltage drop and turns off the oil pressure light. If the key is in the RUN position and the oil pressure switch ever opens, the PCM assumes the engine is out of oil and shuts down the fuel pump. At that point it will set a P0520 Engine Oil Pressure Sensor/Switch Circuit Malfunction.
To diagnose the problem, unplug the connector at the oil pressure switch and check for voltage on the colored wire (black is usually ground wire) with the key in the RUN or START position. Next, check for ground on the black wire. If both check out, check the condition of the oil pressure sensor. Replace if necessaryPosted on by Rick Muscoplat