No oil pressure

Need to have pressure verified with a pressure gauge hooked to it . Worn pump or bearings are a possibility .

What engine size , because could have come with a few different ones ? Engine oil pressure sensor is a input to the PCM - engine computer . This will turn on check engine light if thier is a problem ! What is the problem your having , oil light on , oil pressure gauge not working ?
Engine Oil Pressure Gage
The instrument panel cluster (IPC) displays the engine oil pressure as determined by the powertrain control module (PCM). The IPC receives a class 2 message from the PCM indicating the engine oil pressure. The engine oil pressure gage defaults to 0 kPa (0 psi) or below if:
• The PCM detects a malfunction in the engine oil pressure sensor circuit.
• The IPC detects a loss of class 2 communications with the PCM.

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

Sounds more like an engine idle issue than a oil pressure issue. If the engine idle drops too low, the oil pump cannot provide sufficient oil pressure. If there is no oil light when the engine is idling normally, then there is no problem there.

Possible causes
- Low oil level or motor mechanical fault
- Faulty oil pressure sensor
- Oil Pressure Sensor harness is open or shorted
- Oil Pressure Sensor circuit poor electrical connection

When is the code detected?
The P0521 is detected when the signal sent from oil pressure sensor to PCM goes out of range.
Possible symptoms
- Engine Light ON (or Service Engine Soon Warning Light)
- Oil pressure warning light ON.
P0521 Chevrolet Description
The PCM continuously monitors the engine oil pressure. The Oil Pressure Sensor/Switch sends a signal to the PCM when the engine is running.

Low oil pressure could be the reason the oil light in your car will come on. Test your oil pressure. Without enough pressure, the oil will not reach necessary areas of the engine. The oil pressure sensor itself may sometimes become clogged with sludge from the engine, especially if the engine has not been properly maintained. A clogged oil sensor can give a false reading of low oil pressure, which will illuminate your oil light. So, check the oil pressure sensor light.

• This may be an oil pressure light in which case you need to inspect and or replace the Oil Sending Unit. Located towards the bottom of the engine. When these go bad the pressure will not stabilize and can damage your engine.
• There is also a service bulletin to look at before replacing the unit.

• TSB NO: 08-36-99
• SUBJECT: Engine Oil Pressure Light Flicker
• DATE: Oct. 15, 1999
• OVERVIEW:
• This bulletin involves adding a terminal/wire/vent to the oil pressure switch connector.
• NOTE: THIS BULLETIN APPLIES TO VEHICLES EQUIPPED WITH A 2.7L ENGINE.
• SYMPTOM/CONDITION:
• With a hot engine the oil pressure light may be on or flicker on at idle.
• DIAGNOSIS:
• Verify engine oil pressure as described on page 9-21 of the 1999 Concorde/Intrepid/LHS/300M service manual (Publication No. 81-270-9140). If engine oil pressure is within specification perform the Repair Procedure.
• PARTS REQUIRED:
• Qty Part No. Description
• 1 05017800AA Wire Terminal/Vent

Regards, Tony

Check the oil pressure sensor and the wiring to it.

Oil Pressure Sensor Removal & Installation 3.4L & 3.5L Engine To Remove:

1. Disconnect the battery ground cable.
2. Raise and safely support the vehicle.
3. Disconnect the electrical connector from the oil pressure sensor.
   
   
4. Remove the oil pressure sensor from the engine.

To Install:

1. Install the oil pressure sensor on the engine. Tighten 12 ft-lb (16 Nm).
2. Connect the oil pressure sensor electrical connector.
3. Lower the vehicle.
4. Connect the battery ground cable.
5. Start the engine and check for leaks.

3.6L Engine To Remove:

1. Disconnect the oil pressure sensor electrical connector. Oil pressure sensor 3.6L
   
   
2. Remove the oil pressure sensor.

To Install:

1. Install the oil pressure sensor. Tighten 15 ft-lb (20 Nm).
2. Connect the oil pressure sensor electrical connector.
3. Check for leaks.

Low Engine Oil Pressure

The oil light is signaling low oil pressure in the engine's lubrication system. You say that you have checked the oil level in the engine and it is ok.

The oil pressure needs to be checked with an oil pressure gauge. (It is most unlikely that the warning light is faulty).

Should the oil pressure prove to be low - as I expect it will - the cause needs to be investigated. It is likely that there is a malfunctioning or failed oil pump or the oil pressure relief valve is sticking in the fully open position.

Failure to change the engine oil, at least at intervals stated by the manufacturer, will result in severe oil degradation and reduced oil pressure. However this is usually not enough to trigger an oil pressure warning light.
If you have changed the engine oil in the last six months or so, and have not done over about 7000 miles since then, oil degradation should not be contributing to the low pressure problem.

If the oil pressure gauge check confirms low oil pressure I suspect, on further investigation, that you will find a problem with the engine's oil pump.

You will need to get your vehicle to a reputable auto service shop to have the oil pressure checked and the problem investigated. Do not drive the car in this condition (except to get it to the repairer). The engine is not receiving sufficient lubrication and you run the risk of expensive engine damage and total engine failure.

Hope all goes well with it. Cheers.

If the oil light is on it's one of 2 things: You have no oil pressure, or the sending unit (also known as the oil pressure switch) is defective and is reading no pressure when there actually is normal pressure. You should always assume it means no pressure, because driving it this way will ruin the engine.