Thanks for the feedback Richard, funnily enough I looked at the wiring diagrams (which only seem to show the downstream sensors!), but I noticed that fuses 13 and 14 seemed to be a common factor. So the first thing I looked at today was fuse 13 and guess what it was blown. I replaced it and it blew again. So I am in a way quite relieved as the obvious common problem seems to be a great starting point. So my question is could this be a shorted heater circuit - does that happen?? or do you know of any obvious places to look to trace the short? Thanks again
