I have a bit of a long tale on this one so please bear with me and i will try to make it as easy as posible.

Its an astra 1.4 petrol our customer bought a week or so before it came in with EML on.

We found code for 02 sensor b1 s1 and also pipe between MAF and intake split.

The firm who he bought the car from payed for a new pipe and we fitted it and reset the light/codes.

A week later it came in with light on again , i left the codes in and scoped the sensor. It had no activity but after clearing the code it worked fine??

Back in a week later with no activity at all again ,same code this time sensor had good earth,and battery voltage correct, heater wire ok but no signal. Flat lining at about .075v

Fitted new NTK sensor and all was good, .2-.8 signal. Happy customer.(one strange thing i noticed was the plug was full of engine oil so i cleaned it out)

2 weeks later and its back in, same code.

New sensor appears to be dead??? The last sensor i took off looked new too, why is it so??

If the wiring or ecu was at fault wouldnt it still give a signal? I have 4 wires. One earth,one 12v with ignition on and 14 with engine running. A heater wire and signal wire with 0.075 output engine running at 2000rpm warm.

Could this be caused by overfuelling as i tried to rich the mix by spraying some brake cleaner down intake, this had no affect apart from causing the engine to die a bit. scoped Maf to find its a little rough but seems to do as expected. On solus it says no1 lean mix .01 ish and no2 rich .6v ish

i have took note of code but forgot to bring it home. I was not heater related or open circuit.

My boss believes it could be a faulty sensor but i dont think so as the original sensor looked like new.? I think fitting a new one will only be a short term fix.

any thoughts or help would be great.