Oil pressure light comes on? - 2007 Pontiac Grand Prix GXP Sedan

Oil pressure sensor, or most likely, oil level sensor, either sensors, wires, or connections.

The oil light comes on when the oil pressure sensor detects low oil pressure. The amount of oil has little to with it, although very low oil levels can cause loss of oil pressure. The best thing to do is to have the engine's oil pressure checked with a mechanical oil pressure gauge to ensure that the oil pressure is sufficient at all operating speed and temperatures. If the oil light is still flashing on and off and there is no indication of low oil pressure by the gauge, then replacement of the oil pressure sensor is recommended.

You need to find out why you have low oil pressure. It is normal that as engine rpm's increase, the oil pressure will rise- the oil pump is moving oil faster. Even though your light goes out, you could still have critically low oil pressure. There should be sufficient pressure at idle to keep the light off. The light will come on when your oil pressure is almost nil- I believe for some it's as low as 8 psi. Normally, oil pressure at idle is specified anywhere from 15 to 40 psi. You would have to check specifications for your Expedition. To verify oil pressure, hook up a mechanical gauge at the oil pressure sending unit on the engine block. Check with a local shop.

The causes run from easy, simple to budget busting ruin. Low oil level, wrong grade oil, real old oil, oil leaks, internal oil leaks, worn oil pump, worn crankshaft bearings. It was pretty common on older very high mileage cars to have a fluttering oil light at stops and idle. It was time for a rebuild, or time to look for another car.

The oil light has nothing to do will oil level, but rather oil PRESSURE. If the engine oil is full and there is no rattling or banging noises in the engine, chances are the oil pressure sending unit is bad. If noises accompany the light, then shut down the engine and troubleshooting the engines internal lubrication system.

Oil lights typically come on because low oil//low oil pressure. Check oil level and add if needed, then recheck to see if the light is on or not. Hook up a manual oil pressure gauge to check the pressure. Do you have an oil leak?

Possible causes of the oil light coming on are -
low oil pressure
dirt in the passage behind the oil pressure switch
a faulty oil pressure switch.
Most people either replace the switch or have the oil pressure checked with a mechanical gauge.

There may be a misunderstanding here.
Yes the warning light comes on when the oil pressure drops below 5psi.
If the light comes on and the switch is working correctly, the oil pressure is not good. Any problem with the pump or the screen would make the pressure not good.
If the oil pressure has been checked with a mechanical gauge and it is above 20psi, the switch or the wiring could be faulty.
You would need to have the pressure checked to know.

Does the oil light come on BEFORE the engine shuts down? I have to ask because it is NORMAL for the oil light to be on when the engine is not running. I had a customer that said the same thing just last week. After we wasted a bunch of time (which the customer ended-up paying for) checking the oil level, the oil pressure, and verifying correct oil pressure gauge, light, and sending unit operation, it turned out that the crankshaft position sensor was bad and causing the engine to shut down and it had absolutely NOTHING to do with the oil light - it was functioning as designed.

If the oil light is coming on before the engine shuts down, the first thing you need to do is check your oil level. If the oil level is OK, you need to check the oil pressure with a gauge to determine if there is an actual engine oil pressure problem or if the oil pressure sending unit, gauge or light is malfunctioning. Also, it is highly advisable to not drive the vehicle AT ALL if the oil pressure light is coming on while driving until the cause of the light coming on has been determined and repairs have been made. Otherwise, SEVERE ENGINE DAMAGE may result.

the oil light is coming on due to sensed low engine oil pressure, this is not a level issue unless u are about 3 quarts low, oil pressure indicators don't leave any computer codes, so who ever told u that is wrong, u need to test the oil pressure with a mechanical gage when the oil light is on, until U need to confirm that u don't have a real pressure issue here or you can burn out the engine bearings, if the pressure checks ok then rplace the oil pressure light sending unit in the engine.

This is the pressure light, nothing to do with the oil needing to be being changed, you have low oil pressure being indicated, this will destroy the engine if the light is really indicating low oil pressure, have the oil pressure tested with a mechanical test guage at a shop, if the oil pressure is ok then replace the oil pressure light sending unit.