Hi Peter,

Fault Code PO 132 (MAF) for those who are wondering. Do not fully understand your question but you should have 4 wires on the O2 sensor as follows:

2 will be earths therefore >0.25v
1 Heater wire therefore battery voltage
1 Signal wire at 0.2 - 0.8v approx at 1 htz at idle (approx)

So...is the earth wire actually switching as you suggest? Nice to 4 gas emissions at idle and fast idle...

Regards

Pete M