I have looked into the internal filter for this type of pump further.....
This filter may be filtering the fuel before it returns to the tank.
In the video a pressure gauge is used, I believe it may be teed into the line between the main filter and the hp pump.
Reading Over 6 bar pressure with blocked internal filter. About 4.5 bar after internal filter replaced.
It appears blocked internal filter may cause rail pressure to be higher than target pressure , enough to trigger p0089.
