What's the test on the car?
Neither of the sensors I've had fitted gave a fault through the ECU (until I started up with the sensor disconnected).
From what I've managed to find out on the net the sensor produces a voltage of between 0.1 and 0.9v from a comparison of O2 in the exhaust and in the air. (Some have heaters in order to get to work quicker, I take it the Beat has a heater)
The voltage produced forms a signal to the ECU which adjusts the fuel pulse width according to the signal voltage. The fuel air mixture flicks between lean and rich giving a mean average of correct fueling.
The sensor fails in 2 main ways:
1. It gets coated with dirt from the exhaust gasses(particularly if the car is burning oil). This will tend to reduce the measured O2 in the exhaust so the ECU will reduce fuel giving an unrequired lean mix. This is hot and will damage the valves and cat as well as increase overall wear to the cylinder bore. I'm not sure how the Beat ECU reacts to this but apparently if the measured difference in O2 becomes TOO great (unrealistic) the ECU will read an error and disregard the signal giving an uncompensated, rich mixturre. (I guess this is a fail safe to prevent the above list of damage)
2. Over time the voltage produced drops off as the sensor ages. This gives the effect of sending an overall lean fuel signal to the ECU ALL the time. The ECU compensates by throwing in more fuel this increases the carbon buildup on the sensor, see note 1.
So eventually a fault will show up through the ECU BUT with one or two problems first! All in all this little sensor can, if not working right, cause all sorts of problems, many of which I've seen experienced on these boards. I guess the next question is how much are they and is there a special tool for getting them out?
If it ain't broke, take it apart and see how it works
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) I'll see what I can do but it depends on how tight the thing is. No rush though she seems to be working fine at the moment.
