This is a 4 wire O2 connector: 2 dark brown, 1 light brown, 1 purple. Part#25312184.

This is replacing my '90 O2, so I don't have the schematics.

Thanks for the help.

 

You probably won't be able to use it. You'll actually need just a 3 wire sensor.

The two dark brown are your power and ground for the heater, the purple is the signal wire. The problem is that the 4th wire is something from the ECM that is has to have in order to work. I don't know if it's a reference voltage or what, but it doesn't work without it.

 

Oh poop. And I thought I was so smart. I may have seen in another thread about a 5 volt reference on those years.

BUT - Wouldn't the reference be going to the ECM? If the ECM doesn't expect a signal, which mine doesn't, I don't need to send it one. I am assuming this 5 volts is to test that the sensor is functioning properly. If it is out of voltage range, then the ECM sets a code that the sensor is defunct.

thanks.

 

Well, I obviously did not get much feedback on such a simple request. So, I went and researched the hard way:

Except for on 1% of ALL cars, the 4th wire is just a ground for the O2 sensor. The other 2 are are for the heater. It will work just fine on my 90. AND I paid LESS than crummy after market ones.

Good for me, I'm glad I'm sooooo smart. :yesnod: