So just tack the earths to the stereo earth then

Thats great many thanks chap, I will let you no how i got on

The sensor is the best £15 i have ever spent! Not only did it make the thing work with the chip but its now so much more resposive and my fuel economy has nearly doubled! It used to cost me £50+ to drive to Cornwall from here but i did it for £30 the other week Paid for itself just on the one trip