Could I have O2 sensor problems??

[Jimbo]

Hello people,
I've noticed in the past few months that my car has been a bit cack on fuel economy. Also I have an Autometer air/fuel ratio gauge and the reading on it seems a bit strange sometimes. In the same journey and conditions, ie booting it in 4th I sometimes get a really rich reading and sometimes it reads around the stoich area both with WOT at the same revs.
Also, occasionally the display leds on the gauge go quite dim and don't seem to react very quickly. The car runs fine but I was wondering if this could mean my O2 sensor is knackered?

If it is do I have to go Toyota or will a Halfords jobby do?
How much are they?
Where does the 4 wire cable coming off the sensor lead to so that I can fit a new one?
How long do O2 sensors normally last on these cars?
Is there any other checks I can do and is there anyway of cleaning it?

Cheers

Jimbo

[JJ]

Crap mpg will be related to the current climate of being cold all the time, so the enrichment in the cold start will be quite high = using more petrol.

The 4 wire 02 sensor is a heated one, with two earths and 1 lambda signal to the ecu.

If you trace back the pin out to the ecu, carry otu a multimeter test and test its voltage output.... should be between 0.10v and 0.99v.

If it has no output, then its bu88ered.

If your a/f gauge is working then its likely that theres not a problem.

Normally on a 4 wire type o2 sensor, when the heater part of it breaks down, it chucks out an error code, so you can check if theres any stored.

[Jimbo]

Cheers JJ. If the sensor is fooked, is it the turbo sensor the same part as on a uk NA model??

Also how do you unplug the cable end of it?

Cheers

Jim.