P0521 is a bad signal from the oil pressure sensor (#12603780). Commonly it's a bad sensor, but it also can be a bad 5 volt or ground connection or even a bad PCM. First check the oil level as low oil can set the code. Next would be to use a manual gauge installed in place of the sensor to be sure you have the correct oil pressure. Then test the 5 volt and ground and then install a new sensor. To do the testing you remove the engine cover, then look at the intake manifold on the throttle body side, at that corner of the lower intake you will find the sensor. Remove it and attach the pressure tester there, start the engine and get it to operating temp, does it have at least 24 psi at 1,000 rpm, 35 psi at 2,000 rpm and 38 psi above that? Yes, oil pump and bottom end are good. No, start looking deeper. Next take a voltmeter and check the connector for the sensor. Check between pins 1 and 2. Do you have 5 volts? Yes, short pin 3 to pin 2 does the gauge react? Yes, wiring is intact and you have a bad sensor.
Images (Click to make bigger)
Wednesday, December 3rd, 2025 AT 10:59 PM
