See videos .

https://www.youtube.com/results?search_ ... k+solenoid

Mine was similar, you might have to drop rad and intercooler out the bottom together, you should be able to get to the sensor.

I would reinstall the original parts and see if those codes go away. Your 'parts cannon' approach will become very expensive, stop buying parts. It needs a proper diagnosing, not just "it kinda sounds like". Get a new mechanic. A smoke test will detect vac leaks, but theres no diagnosis po...

https://charm.li/Volvo/

same as all/data.

I think I paid $225 for a new rad last year.
A warped cyl head is far worse.
Order new transmission line clips and O rings too.

its not as if the engine blows up if you get them reversed, try it and find out.
It should work both ways because the connector tabs on the new horn are not 'keyed'.
Worst case is you pop the fuse.

window heater wire sounds likely, that was the scene of the repair. I don't think the rear window heater is part of the tailgate closed wire path. There should be a separate wire film pattern on the rear window with a different set of wires going to it, the pink wire from the 54/50 connector and a ...

did you install new o rings on all the injectors and apply lube ?
try spraying brake cleaner around the seals at idle to check for leaks.

Its timing related, not necessarily timing belt, can be caused by old/wrong engine oil , dirty oil filter, causing the vvt response to lag. If you have vida you can run the cvvt response test, it will tel you if its lagging, responding too slow. I did it on mine and it failed the test, a simple oil ...