engine light on and code indicates the heater circuit in the 2nd 02 sensor faulty (the one under the car after the cat). It has two white wires, a grey and a black. I have established that the two white wires are heater circuit. if I unplug sensor and test the two white wires on the sensor with a multimeter it shows no continuity. If i do the same with the other 02 sensor (the one on top on exhaust at front of engine) it shows about 10 ohms. So that seems to verify it needs a new 02 sensor under the car. So i have been having a look but some of them online show the wire colours in the plug in a different order. Mine has the two white next to eachother at one end of plug, but some I see have one of the other wires between the two white ones. This is making me think i need to be very careful to get the right one. are both sensors on the car the same or is the 2nd sensor different spec to first one? can anyone recommend one with a link to it. I don't want to spend more than neccessary but it has got to work. I don't know if people have real problems with the cheap ones. car drives fine, i believe this sensor has no effect on the car, it is just there to monitor effectiveness of cat. but MOT due and light keeps coming back on when turned off. It's my brother's car, he has very little money and I am trying to help him out . Please provide any advice you can. Thanks . (I'm impressed how well this car goes, seems to have a lot more go in it than a Fiesta 1.25 of that era.