Do i have to take the motor out to change a oil pump in my 2003 ?

I see more than one issue in your story. Its possible the computer lost memory and will need to relearn. But that would not explain the knocking noise. The oil pressure warning might explain the noise if oil pressure really is low. Running without the belt for even 5 min would not cause the problems you describe.
I would focus on the low oil pressure warning and the noise first.

Is this high mileage vehicle? If so, I doubt changing oil pump will help, you may need engine overhaul?
Sometimes, you use an analog pressure gage in place of the oil pressure sending unit, to read actual oil pressure. My info says at idle, oil pressure 4.3 psi or more. At 3000 rpms, it says 43--78 psi.

Check your oil levels. If full, then confirm pressure with an external oil pressure gauge attached to the motor.

You may need to tow it to a Repair shop to keep from ruining the motor. When stuff like this happens, it can be a defective oil pressure switch. But it can be a bad oil pump or bad bearings.

Sometimes an oil sample needs to be done or just change the oil. If gas mixed with oil, then the oil is too thin to pump good. And it is time to find out why gas is in the oil.

I hope my solution is helpful and that you will rate me.

That would indicate either a faulty oil pressure sensor or that the oil pressure is low. This would be caused by a faulty oil pump, partially blocked oil lines or lack of oil. Check and re-check oil levels whilst the vehicle is on a flat piece of road. Check you have the right oil dipstick for the car (it may have been replaced with a longer oil dipstick which would give you a false reading) or even that the engine may have been changed at some time! make sure you have used oil of the right viscosity (check the owners manual). If that doesn't fix it then give the engine a good flush out with flushing oil to clean out the oil feed system. refill with fresh oil. If that doesn't sort it, change the oil pressure sensor. (on the engine block). Get the engine diagnostics readout done to see if there are any error codes stored. If you still have problems then it may be the oil pump which will cost a lot of money to change!

The oil pump could be bad, or going bad. Oil pressure is effected by wear on the crankshaft main bearings and camshaft/s bearings. If those bearings are bad, that would make it lose oil pressure, but I wouldn't think it's time for a new motor at that mileage!!! I would find out what the actual oil pressure is, using a "wet gauge" or oil pressure gauge. The oil pressure sending could also be bad, giving false readings.

I would check your fuel filter first. If the car idles fine and drives fine under a little throttle then your filter could be the issue. If this does not solve the problem you need to take a look at the fuel pressure regulator and the fuel pump. Put a fuel pressure gauage on the car and rvie it. If you see large dips in the pressure it is probably the pump failing. You can put a might vac on your furle pressure regulator, if it holds vaccuum then it is good. I am willing to bet your fuel filter(s) are clogged.

When the oil is cold it is thinner or watery and the pump moves more oil as it turns making the pressure go up. As the oil warms up it thickens and the pump moves less oil letting the pressure go down. Increasing the engine speed makes the pump turn faster, therefore it moves more oil and the pressure goes up. Changing oil grades will change the numbers somewhat, for example 10W40 will give you different readings than 5W30. I don't see any problem with the readings you put in your posting. I wouldn't be concerned until the warm idle pressure gets down to about 30 or a little lower. Hope this helps.

This is pretty common on the older vehicles. There are three primary things it can be.

1. The wear in the bearings is enough to bleed pressure to the point at low pressure it just won't stay up high enough.
2. You have a bad sensor
3. Your oil pump is not pumping enough pressure.

Most of the time you don't have to worry about it. I would go to a heavy weight oil like 10W40, and I would switch to full synthetic. It works great on older motors.

Hope this helps.

it could be crank bearn or cam bearm they are noted for it

Try hooking up a mechanical gauge to make sure you have a problem.