Q: The oil pressure is fine but when I crank the car and when it warms up it drops down to maybe 20 and starts knocking a little. Whats wrong?

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Is it oil pump or pressure sensor

My car has 161407 miles.
My car has an automatic transmission.

The first step is to check the level of the oil. Assuming it’s full, and there are no leaks on the system, it could be the pump or the sensor. The easiest way, despite that you need a special tool, is to hook up a gauge inline and test the oil pressure. This will allow you to see if you truly have a pressure issue or if the electronics are to blame. This gauge will replace the oil pressure sensor/switch. Remove the switch, thread in the sensor (carefully, and snugly), and start the vehicle. If the pressure is below the ratings for your vehicle, and the oil level is full, you will want to replace the pump. You will also want to make sure the passages are clean and sludge free. Bent, damaged, or clogged oil lines can also cause pressure issues. If the pressure is where it needs to be, the issue is the sensor and it should be replaced.

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