Hi Geoff, I have the same problem on my S-Type but the amber light does go off and then periodically returns. I have been told that driving it over 2000 revs for at least 30 minutes will clear the problem as it apears to be a problem with the catalysor. As there appears to be no drop off in performance and if the car runs Ok as mine does it seems it's nothing to worry about. I had a diagnostic done by a Jaguar dealer but they found nothing wrong - still it's makes me feel uncomfortable driving with this amber light on as I suppose it does you.