Engine oil pressure light stays on - 1989 BMW 5 Series

The low oil pressure warning lamp will illuminate anytime the ignition switch is turned to the ON position without the engine running. When the engine is running, the light also illuminates if the engine oil pressure drops below a safe oil pressure level. To test the system, perform the following:
If the oil pressure light does not work, perform the following:

1. Turn the ignition switch to the ON position.
2. If the lamp does not light, check for a broken or disconnected wire around the engine and oil pressure sending unit switch.
3. If the wire at the connector checks out OK, pull the connector loose from the switch and, with a jumper wire, ground the connector to the engine.
4. With the ignition switch turned to the ON position, check the warning lamp. If the lamp lights, make sure the oil pressure switch is properly grounded in the cylinder block, and if so replace the oil pressure switch. If the lamp still fails to light, check for a burned out lamp or disconnected socket in the instrument cluster.

To diagnose an oil pressure light that stays on, perform the following:

1. Check the engine oil level and top off as necessary. If the engine was 2 or more quarts low on oil, test start the engine after topping off the oil level and recheck the oil pressure light operation. If the light stays on, stop the engine immediately and go to the next step.
2. Disconnect the wire at the sending unit, then turn the ignition switch to theON position. If the light remains on, check the wire from the sending unit to the gauge for being shorted to ground and repair as necessary. If the light goes out, turn the ignition switch OFF and go to the next step.
3. Replace the oil pressure sending switch with a known good switch.
4. Start the engine and check the oil pressure light operation. If the light stays on with the engine running, stop the engine immediately to avoid severe engine damage until the cause of the problem can be determined.

WARNING
If the oil pressure light remains on while the engine is started, stop the engine immediately. Do not operate the engine until the cause of the problem can be determined. Operating an engine with low oil pressure will cause severe internal damage.

Possible causes for an oil pressure light to stay on are:


Pinched or grounded sensor wireDefective oil pressure sending unitRestricted or severely leaking oil filterExcessive internal engine bearing clearance.Insufficient or severely contaminated engine oilBlocked oil pump pickup screen or severely worn oil pump

The light is activated by an an oil pressure switch. With the engine not running there is no pressure so it lights up. When the oil recirculates, the pressure increase and the light goes out. Locate yours and change it, they are fairly inexpensive. If it stays lit after a change it may indicate something more serious.

The oil light is not an indication of oil level; rather it is an indication of oil pressure. If the oil pressure is low enough to light the oil light, you should be hearing some rattling in the engine. Otherwise, it is possible that the oil pressure sending unit is defective. You are lucky if that is the case, because some vehicles are wired that if the oil pressure sensor indicates low pressure, the engine will shut down to protect itself. You should have the oil pressure checked with a mechanical gauge ASAP and take whatever corrective measures are necessary.

Check the actual pressure, with a guage.
This is usually done via the oil pressure switch hole. It the engine has fewhoudrs then the oil bypass valve is stuck in the open position.
This is located inside or as a part of the oil pump itself.

Your vehicle may have an "oil level" sensor built into the oil pan. If so, and the sensor is bad, the dash will constantly tell you that the engine needs more oil even if it does not. Checking the oil with the dipstick, a minute after the engine has been turned off on level ground is always the best way to check your oil. Try scanning the vehicles computer systems to see if there are any fault codes. The warning light may also be on a timer that just needs to be reset. The "Check Oil" light should be separate from the engine oil pressure warning light. As long as the engine oil pressure light stays off, you should be ok. Checking the oil pressure with a manual gauge would be a good idea as well.

The oil light is supposed to come on when there is low oil pressure, so when the car starts, the pressure goes from 0 to whatever (25-60psi depending on the engine). As a result, the light stays on for a few seconds at the beginning of the start cycle and is then supposed to go out. If the low oil pressure light remains on, then you either have low oil pressure or you have a sensor problem. If you have low oil pressure, you may need a new oil filter. If the filter was just replaced, then you need to get professional help because low oil pressure will wreck your engine in a hurry. Your engine's oil pump may be faulty and need to be replaced.

That could be from not having any oil pressure "oil pump failure, clogged filter, etc" or from a faulty oil pressure sending unit. More tests would need to be performed but is it really an oil pressure light or is it the change oil light. More info would be needed

If the engine is not making any noise then it is likely not a real oil pressure problem. Just to make sure have the pressure checked by a shop with a mechanical test gauge and if found to be inspect replace the sending unit and that should in most cases cure the problem. I assume this is a pressure indicator.

there is always the possibility that you really have low oil pressure when you get this light, at idle the engines oil pump produces the least pressure and if there are problems then that is when it shows up, so have the oil pressure tested by a shop with a mechanical test gage, if the oil pressure is within spec then replace the oil pressure light sending unit on the engine, I don't recommend you drive this until u are sure of the pressure, u can SEVERELY damage the engine is the pressure is really low.

I think you have a suspect oil pressure sender unit. Replace it as they are cheap and need to be reliable and it will be cheaper than getting the oil pressure tested. If the light still stays on with the new sender you may have internal wear or a partial blockage. If the light stays on you need to have it urgently checked by a mechanic or you could risk serious engine damage.