The BMW 330CI engine oil pressure warning lamp is lit.why?

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

May be due to oil pump wear, filter blocked by dirt, oil filter is exposed out of the oil surface, the oil level is low, the oil mixed with air and the pressure gauge is caused by the failure of the. In addition, the oil viscosity is low, the oil seal and poor lubrication, lubricating oil viscosity is too large, too cold oil sludge deposition too much also can cause the oil pressure indicator display abnormal.
source: obd2 tool car diagnostic

"Check your license plate lights" The red lights on each side of the trunk open indicator

Sounds like a fuel problem check fuel pressure at fuel rail. Possibly pump or pressure regulator.

Fig. 1: Location of the oil pressure switch-3.3L and 3.8L engines




Fig. 2: Location of the oil pressure switch-3.0L engine

Fig.: Oil pressure switch (sending unit) schematic


The low oil pressure warning lamp will illuminate when the ignition switch is turned to the ON position without the engine running. The lamp also illuminates if the engine oil pressure drops below a safe oil pressure level. To test the system, 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 still fails to light, check for a burned out lamp or disconnected socket in the instrument cluster.

REMOVAL & INSTALLATION
On the 2.4L engine, the oil pressure switch is located on the side of the engine block facing the firewall. On the 3.0L engine, the oil pressure switch is located on the oil filter adapter housing, next to the starter motor. On the 3.3L and 3.8L engines, the oil pressure switch is located next to the oil filter.

1. Locate the oil pressure sending unit on the engine.
2. Disconnect the negative battery cable.
3. Disconnect the pressure switch electrical harness.
4. Using a pressure switch socket, deep-well socket or wrench, loosen and remove the pressure switch from the engine.

To install:

1. Install the pressure switch into the engine and tighten securely.
2. Attach the electrical connector to the switch.
3. Connect the negative battery cable.
4. Start the engine, allow it to reach operating temperature and check for leaks.
5. Check for proper oil pressure switch operation.

Hope this helps (remember to rate this answerr).

I have a 1999 Ford Expedition with a 5.4L Engine and don't know what you are talking about. I searched under mileage sensor for the 99 expedition but could only find On-Board Warning Systems.

Are you talking about the Vehicle Speed Sensor?

If so, this is located near or on the transmission and has wires that go into the harness, and basically is a pickup coil that detects movement of the transmission which then controls mileage on the odometer and the speedometer.


On-Board Warning Systems Turn on the ignition switch in almost any vehicle and watch the instrument panel. The modern automobile has an abundance of warning lights that provide valuable information. The list could include:

Brake system warning

Windshield washer fluid level

Coolant level

Brake fluid level

Door ajar

Headlamp door position

EGR or Check Engine

High beam indicator

Seatbelt light

Cold engine warning

Turn signals

Charging system

Transmission temperature

ABS or Anti-lock Brake System

SRS or Supplemental Restraint System

Brake lining wear indicator light. The high price of fuel created a demand for yet another light--the fuel economy warning system. When the light comes on, it tells the driver he or she is pushing too hard on the gas pedal. High manifold vacuum equals good gas mileage and vice versa. The system simply reads manifold vacuum from a sensor, and when it drops to a predetermined level, a circuit is completed and the light is lit. This has become in many models what is known as the up-shift light. An arrow on the dash indicates the time to shift into the next gear to obtain optimum fuel economy. If a warning light comes on, you must find out why. It means there is a problem either in the system being monitored or in the warning lamp circuit. Finding the actual fault is important and not very difficult. However, a wiring diagram may be needed to prevent confusion. Looking at the typical warning light circuit, you'll see that the bulb is most often supplied with current through the ignition switch. Further examination reveals the most common way of completing the circuit and getting the bulb to light is by means of a sensor, which completes the ground connection. In this case, sensor is a fancy word for a switch that turns on or off according to specific conditions. Consider a typical oil pressure warning light system. Current from the ignition switch flows through the warning lamp and from there to ground through the oil pressure switch. This particular switch is normally closed and the circuit is complete until the switch opens in response to oil pressure in the engine. Just the opposite is true with the coolant temperature sensor. It is normally open and only completes the circuit when an internal element expands (in response to heat) to close the contacts. If the vehicle has a cold engine warning lamp, the sensor includes two sets of contacts. One set is normally closed and opens as the internal element expands. This action breaks the ground circuit to the warning lamp. The other set of contacts functions if the temperature rises far enough to close them, turning on the high temperature warning. If either of the temperature lights is lit while the engine seems normal, just unplugging the wires from the sensor will provide valuable diagnostic information. If the lights remain lit, there's a short to ground in the wiring from the lamp to the sensor. The service needed isn't to the cooling system, but to the warning system. If the lights go out with the wires unplugged and the engine seems normal, it's entirely possible that the sensor has failed and needs to be replaced. Nevertheless, don't just unplug the wires and forget about them. This could be disastrous for the vehicle owner should a cooling problem develop without warning. Fig. 1: Typical coolant temperature sending unit location
Fig. 2: Oil pressure sending units may be located in a variety of places on the engine

install a mechanical guage to test the actual pressure, if its fine the sending unit is faulty, if nor remove the oil pan and check the oil pickup for blockage,

That sounds like you bought big problems. Oil ights indicate low oil pressure= BIG BUCKS. I would have a qualified repair shop check it out, A shop that specializes in BMW. If you are lucky, maybe the oil sender is just bad. They can also check out the Ck eng light. But the oil light is priority one.

You need a new battery, or your battery cables are loose

7 quarts of 10-30 or 10-40(summer) synthetic oil, requires premium gasoline