my check engine light came on, i had it diagnosed, and my oxygen sensors are faulty. im trying to replace them and im finding some online with connections for about 100-120 dollars a pop, whereas i've found some without connections (just wires) for a mere 25-35 bucks each. im trying to save some money so i can put it into a new cat-back exhaust, but i dont know how many wires the oxygen sensor should have. they range from 1-4. im assuming i sensors with two wires coming of them? i've got a 96 disco with 130k miles.

 

Before you replace the O2 sensors, consider cleaning out your engine with a good engine flush and a induction cleaning so it will run better after the replacements have been installed.
As for the O2 sensors, post this question on the LRO and the LRR Forum websites and direct it at Rover X, he can give you the names of cheap ways to go.
Mike

 

You can test your two o2 sensors (before the cat).

The voltage should fluctuate between 0.2 - 0.8V if it does not fluctuate from the low voltage side then you most likely have a bad sensor. If the voltage consistantly stays on the high side then your engine is the one with the issues (maf, injectors, etc...).

White wires are heater wires
Black is signal (positive voltage)
Grey is the ground

Just hook up your red lead on your meter to the black and black lead to grey and set it to 20VDC or 2VDC if you have that setting and make sure your car is running and is warm.

You can also buy o2 sensors for 40.00 but you will have to splice in your connectors.