The secondary air system on this (2008 2.5XT) failed (in a good way; pump siezed, valves stuck shut) at 40000 miles and I have been happily driving it around on the basis of wiping the error on first start up which normally lasts the whole day, (depending on use/weather sometimes another wipe is required). Just recently (now at 125000 miles) the fault has been occurring whilst driving and generally won't clear. From a cold start it will normally clear; it returns after about 5 minutes driving and then won't clear again except occasionally on very long high speed runs it will clear for a while but then returns. (Suggests something temperature related)? The pre and post cat sensors are all behaving themselves (they are new units) and there is no discernible change in performance (at least not as far as I can tell) and the thing runs like a dream; no misfires etc..
I am at a loss as to what is now causing this demand for the secondary air system when in use; presumably this would be either "low temperature" or "high emissions"? Open to suggestions as to what is causing it; and how to kill whatever is causing it! I am simply looking to get back to the original state of clearing it once a day and getting a few more years (and a few more MOTs out of it).
Thanks in advance for anything you can offer.