Evening Bryan,

Thanks for your input. This vehicle is also an AXP engine and the colour codes were reproduced from I think the NTK/NGK web-site. Did about an hour or so researching this but cannot be sure. All measurements were taken from the sensor wires. Now here is the strange thing, the sensor has 5 wires but is connected to a 6 wire connector to the loom. Both connectors have 6 pins so there is a con-joint in the connector. I initially measured the voltages on the 6 wire loom cable and found that the "6th" wire contained a fluctuating voltage of about 0.5v to 2v @ about 1 hertz. This complicates it more for me but could this be the changing polarity you are talking about? I put my hand up and admit that electrics is a weak point for me..

Regards

Pete m

PS...shame that the spell check is not English but American!!