After much contortion and confusion I have hopefully traced my P0171 code to a disintegrated twin vacuum hose on the supercharger bypass actuator. The mystery for me is I am unclear what the device is on the end of one of the hoses:






I would normally associate the construction of the plastic fitting with a check valve of some sort. As far as I could tell it was just dangling amongst some other tubes and wiring and didn't seem to be attached to anything. If anyone has any insight on whether it is in fact a check valve or whether it is supposed to be attached somewhere I would appreciate it. Thanks-

 

HJ808;

I recently replaced this hose on my 07 SV8 and the end you are asking about was left unattached. I do not know the purpose of this feature but the car runs fine.

Best Regards, William

 

Great, thanks for the info-

 

I just replaced mine a month go on my 2008 XJ Superv8, luckily I had some videos of it before it got old and snapped.
it appears to just dangle and not connect anywhere. The code was cleared and it runs great

 

A little more clarity, courtesy of a post from member Brutal in 2014:

"it doesnt go anywhere. thats a capped end and it is nothing more that a small vacuumreservoir"

So, just dangling seems to be correct, but, though I have no standing to second guess the Jaguar engineers, the function as a vacuum reservoir seems a little lost in the way it is configured. I would think that since the split in the hose is at the attachment to the large volume of vacuum just behind the throttle plate and the cannister is just at the end of its own little stub, the very small volume of vacuum in the plastic reservoir would have a negligible effect on the actuator. I wondered at first if mine had been installed in reverse and that the vacuum cannister should have been in series with the actuator, but my guess is that the arrangement shown in the parts diagram is correct.

 

I had something similar on a Roush Mustang.....do the two ends clip together. I was told it was some sort of bypass that shouldn't be used......Car ran fine.