(2004 Stratus 2.7) The oil light stays on until the engine reaches about 1500 rpm. I want to test the pressure with a mechanical gauge. What is pressure at idle and what is maximum pressure (warm engine)?

Hi. Hope the oil wa drained at the recommended service intervals? Have the oil pressure checked with a mechanical oil pressure gauge from cold start up until she warms up. The pressure should be slighly higher when the oil is cold. But keep the rpm in that range, and see what the pressure gauge shows.

Could be a problem with the oil pump, the oil pressure sensor, clogged oil lines, or something more major.

Oil Pressure Test Check for proper oil pressure at the sending unit passage with an externally mounted mechanical oil pressure gauge. A tachometer may also be needed, as some specifications may require running the engine at a specific RPM.

1. While the engine is cold, locate and remove the oil pressure sending unit.
2. Following the manufacturer's instructions, connect a mechanical oil pressure gauge and, if necessary, a tachometer to the engine.
3. Start the engine and allow it to idle.
4. Note and record the oil pressure reading when the engine is cold. The engine may need to run at a specified RPM, if so check the vehicle's specification.
5. Run the engine until normal operating temperature is reached.
6. Check the oil pressure reading again with the engine hot and record the value. Turn off the engine.

Compare the hot oil pressure reading to the specification. If the reading is low, check the cold pressure reading against the specification. If the cold pressure is well above the specification, and the hot reading was lower than the specification, the engine may have the wrong viscosity oil. Change the oil, making sure to use the proper grade and quantity, and then repeat the test.
Low oil pressure readings could be attributed to internal component wear, pump related problems, a low oil level, or oil viscosity that is too low. High oil pressure readings could be caused by an overfilled crankcase, too high of an oil viscosity or a faulty pressure relief valve.

Look for the oil pressure sending unit on the block or the cylinder head on the V-6 or V-8 models. --- OIL PRESSURE TEST Check for proper oil pressure at the sending unit passage with an externally mounted mechanical oil pressure gauge (as opposed to relying on a factory installed dash-mounted gauge). A tachometer may also be needed, as some specifications may require running the engine at a specific rpm.

1. With the engine cold, locate and remove the oil pressure sending unit.
2. Following the manufacturer's instructions, connect a mechanical oil pressure gauge and, if necessary, a tachometer to the engine.
3. Start the engine and allow it to idle.
4. Check the oil pressure reading when cold and record the number. You may need to run the engine at a specified rpm, so check the specifications.
5. Run the engine until normal operating temperature is reached (upper radiator hose will feel warm).
6. Check the oil pressure reading again with the engine hot and record the number. Turn the engine OFF.
7. Compare your hot oil pressure reading to specification. If the reading is low, check the cold pressure reading against the chart. If the cold pressure is well above the specification, and the hot reading was lower than the specification, you may have the wrong viscosity oil in the engine. Change the oil, making sure to use the proper grade and quantity, then repeat the test. Low oil pressure readings could be attributed to internal component wear, pump related problems, a low oil level, or oil viscosity that is too low. High oil pressure readings could be caused by an overfilled crankcase, too high of an oil viscosity or a faulty pressure relief valve.
   

have a mechanical test gauge put on the engine to verify you have good oil pressure, if it is ok then replace the oil pressure sending unit on the engine

Sounds like the oil pressure sending unit needs replaced.

engine oil pressure may be low remove oil pressure sending unit and install a pressure gauge check for pressure while warm if pressure is ok replace oil pressure sending unit oil pressure at idle should be between 5-15 psi at min

Does the oil light come on or the knock occur during the engine warm up after a cold start?
There could be a couple of problems causing the issue. You could have an oil pressure pump or pump pressure regulator sticking. I would have a mechanical oil pressure gauge installed and verify oil pressure at idle and 2500 rpms to make sure oil pressure is in normal ranges.
You could also have excessive piston rod bearing, crankshaft bearing or cam shaft bearing wear that will cause oil pressure to drop too low to prevent the rod knock your hearing at 2500 rpm.
You said a knock and not a ticking noise,so I don't believe a lifter is the issue at 2500 rpm.
Start with the oil pressure check and go from there.
Let me know.
Regards,

CHECK YOU OIL

per the Haynes manual for the 95-05 Dodge Stratus on the 2.0L & 2.4L DOHC 4 cyl engines, the oil pressure sending unit is located at the left end of the rear side of the block. On 2.4L SOHC 4 cyl engines, the sending unit is located at the left end of the rear side of the block. On 2.5L & 3.0L V6 engines, the sending unit is located on the oil filter housing, on the front side of the block. On 2.7L V6 engines, the sending unit is located at the left end of the rear side of the block. To access it, remove the heat shield.