Purchased another 08 supercharged RR for cheap about 2 years ago. Did not move but ran well with crankshaft correlation fault. Front driveshaft broke, easy fix. Correlation fault, not so much. I did hear the chain rattle occasionally, But I decided it was too good to just save for parts, so in we go. Main timing chains were tight, secondary chains looked good as well. Tensioner on bank 1 stuck in collapsed position during a second look 3 days later. Replaced it and retimed the engine. Runs even better now but i still have a correlation fault. I then swapped the timing solenoids to the opposite banks to see if the fault moved with the solenoid, but it did not.
Got my gap tool out and did some comparisons with the other Rover.
"Intake variable camshaft timing" on both banks reads within 5 degrees per bank on both Rovers. "Actual inlet variable valve timing" on the good Rover both banks are the same (0-0.4). On the faulty Rover bank 2 matches the good Rover (0-0.4) but bank 1 reads 9-11 degrees.
Does this point to a faulty camshaft position sensor?

Attached are the graphs that i took from each vehicle.
https://drive.google.com/file/d/1uu8KleuSBdLJXQyMiadj7cq0-FLidDDB/view?usp=sharing
https://drive.google.com/file/d/1DqGWNU90F1wxbjdkeqgwetMbEDuHghjv/view?usp=sharing

Did you replace the cam phasers?

No i did not. Just the sticky tensioner. Chains and guides were all left in place and looked good. I did retime the cams. I do wonder if that is the case. How do i tell if the phaser is trash?
What i dont understand and am trying to figure out is what the signals mean. With only on sensor per bank i would have thought that if the cam sensor is incorrect that the vale timing would also change. but that does not seem to relate. Its like it defaults to a single sensor and changes the timing on both cams together. If you compare the signals from the good Rover to the bad one the cam timing never moves 9 degrees like the questionable signal indicates. It only moves 0-0.4 degrees. Even the cam timing angles only move a few degrees. So I wonder if 9 degrees is even possible without catastrophic engine damage. Also when i unplugged the cam sensor the questionable signal only drops to 5 degrees and not to 0.
Could this be electrickery like a bad ground or something. I am not getting a cam sensor fault only the correlation fault. And also no chain noise since retiming the engine.

I'm not saying this would be a fun job, but might be worth swapping the sensors side to side to see if the issue moves. Pretty clear indication if a sensor is the issue.

I tried swapping the solenoids from one to the other with no change. Unfortunately thats not an option with the cam sensors. I could however take the sensor out of the good Rover to test the signal. BUT:
You got me thinking about the phaser comment, and I remember noticing an anomaly while doing the timing. Before and after resetting the cam timing i noticed that when i turned the engine over the exhaust camshaft would push the intake cam at a certain points and the chain would become slack on the side that should stay tight. However during the rest of the rotation the chain was fiddle string tight. So when i retimed it and saw the loose chain again i simply pushed the guide so the tensioner moved to the next stop. That seemed to solve the issue.
Now that i have spent days watching utube vids on the phasers and learning how the system works. I suspect that the phaser was not locking properly and allowing the exhaust cam to push the intake causing the chain to loosen. And now it is timed in the wrong position which is why its throwing the correlation code.
I also found out that the engine has been replaced when is got into the job. Found a stock number on the front of the timing cover that is not supposed to be there. It is varnished on the top of bank 1 but not equally varnished on bank 2. It also appears that someone may have been in there already since the gaskets were not fully crushed like they should be for the age of the engine. This may have something to do with the phaser being out of time.
So... it looks like Im going back in. At least it will be easier this time now that I know what Im doing. I will open up the phaser to see what i find and decide from there if I clean and reinstall it or replace the lot.

It might take a bit with Christmas and all that, but I will let you know what I find