Hi, I bought two upstream o2 sensors with just wires and no connectors. Does it matter which of the two white wires of the sensor connect to the connector? I'm assuming two white wires are heater and the black one is signal. Also, I was diagnosing my current upstream sensors and one of them close to the radiator is bad however the one close to the cabin (left of the sparkplugs) is working. Since I bought two of the same brand, should I replace both upstream sensors or just the broken one.

 

Might as well replace both. According to Haynes and the FSM, the white wire (for OE parts, anyway) is the signal.

 

white=signal-black is almost always ground-gray=heater
and note: do not merge the two white wires together! terminate one
and splce the other on with the harness

 

Hold on so you are saying that one white and one black wire should be used. The third white shouldn't be? I'm confused. On the current setup, two white wires and a black wire is used for the front o2 sensors.

 

dont listen to theese people a 3 wire will have 2 whites and a black the whites are the heater hook them up there is no right or wrong, the black is the signal. on a 4 wire it is same as a 3 but there will be an extra grey wire it is a ground. it can be used on a 3 wire setup i have a 4 wire o2 sensor on my front bank ( i got it free from work) i left the grey alone, did not ground it, and have no codes and heater circuit is working according to my scanner.

 

Connect white wires to white wires, black to black. It does not matter which white wire from the sensor is connected to white wire to the socket. The white wires are for heater. Black is signal.