S40 1.6D 2008 - Low oil pressure warning light on idle
 

Looks like this problem is hard to solve for me alone.
The car has gone 130 000km.

The car works fine, but the oil light comes on at idle.
When I increase rmp a little, then the light disappears.
The oil level is of course checked and the oil has specifications recommended for this car.

I have dismantled the sump and there doesn't seem to be problems with the strainer and the filter.
I also disassembled the oil pump, but it seems to be okay.

Now I don't know what to do next.

I am grateful for any suggestions that may be helpful in finding the solution!

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a few possible causes 1) issues with the pressure sensor 2) the o-ring/seals in the pump are leaking pressure (sounds like you did the r+r here) 3) the oil pump components are worn and out of spec . It looks like you already cleaned the pick screen etc. As always, make sure you are using the factory recommended oil weight.

Thanks for your feedback mt6127.
How can I check if oil pump components are actually worn and out of spec?
Feels tight when I spin the parts, but I find it difficult to judge when I do not have a reference pump with new parts.

there are clearance values between the pump components that would probably be listed in a full shop manual or the VIDA/DICE software. But, if you are going to to to the trouble of pulling the pump back out to measure tolerances, you might as well simply install a new oil pump. I'd probably start by replacing the oil pressure sensor first, then consider a Seafoam treatment for the oil to see if that removes any gunk and helps restore pressure at idle. If that doesn't help then you probably should put in a new oil pump with new seals/o-rings etc. I am also assuming you followed standard procedures for priming the oil pump upon its reinstall as well.