Hi, we were just working on this error message. Unfortunately the fix was a new print head - this issue can be complex and hidden by other things
that are not working.
In our case, the print head was blown and also mother board. However, the error is due to a mechanical test that the P800 cpu performs to verify correct movement of various parts. We took a board with the 150D error and put it into a know good printer and it still gave this error. After a lot of testing it was the head/mother board combination replacement that fixed it.
I have seen customers who have 150D errors and manual suggests cleaning the head shaft (silver rod), encoder, make sure capping station can move freely (small suction area both updown and front/back). Others have removed AC power cord to printer, wait a few and then restart.
Keep me posted on what you find.