Converting to 3 wire O2 sensor
Thread Starter
Team Owner
Joined: Feb 2006
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From: sw Ohio
Converting to 3 wire O2 sensor
I need to convert to a later style heated O2 sensor since I put ceramic coated headers on my '85. Does anybody know where I can get both the 3 wire connector and the sensor together? Also how is this compatible with an early ECM?
Pro
Joined: Nov 2006
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From: Plano TX
I haven't found one together, but I have seen on ebay tpiparts (I believe) that has the harness and then also you can find pretty good deals on the correct AC Delco sensor there on ebay as well.
As for if it's compatible with the old ECM, basically you have one wire that you run off a 12v source, such as the fuel pump line let's say, then you have one line that goes to ground... finally the last wire goes to the ECM just like the original sensor. Basically you're just adding a heating element to the sensor. The harness I've seen is nice so you don't have to cut and split the o2 sensor wiring if you have to install a new one. The harness is a conveniences piece.
As for if it's compatible with the old ECM, basically you have one wire that you run off a 12v source, such as the fuel pump line let's say, then you have one line that goes to ground... finally the last wire goes to the ECM just like the original sensor. Basically you're just adding a heating element to the sensor. The harness I've seen is nice so you don't have to cut and split the o2 sensor wiring if you have to install a new one. The harness is a conveniences piece.
Thread Starter
Team Owner
Joined: Feb 2006
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From: sw Ohio
As for if it's compatible with the old ECM, basically you have one wire that you run off a 12v source, such as the fuel pump line let's say, then you have one line that goes to ground... finally the last wire goes to the ECM just like the original sensor. Basically you're just adding a heating element to the sensor. The harness I've seen is nice so you don't have to cut and split the o2 sensor wiring if you have to install a new one. The harness is a conveniences piece.
Thread Starter
Team Owner
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From: sw Ohio
Safety Car
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From: Houston Texas
Just remember, the black one is the one that goes to the ECM, and ground one of the white ones and the other white one goes to a switchable source, such as a hot wire to a relay for fuel pump or fans.
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From: Summerland B.C. Canada
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From: sw Ohio
Ok got the parts in, but I have one last question. The last wire goes to a 12v source. What is the best way to wire it in? I dont want to put in the wrong place and put a drain on the battery 
Team Owner
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From: Athens AL
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You could wire it to the wiper motor for example. On my car I might wire it to the MAF relay or cooling fan relay.
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From: sw Ohio
Race Director
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From: oregon
Anyone ever wonder why there are 3 wires? i mean the 02 itself would be a ground since its screwed into metal tubing which goes straight to the block. Anyone know the reasons on this one? just a curiousity thing.
Melting Slicks
Joined: Feb 2006
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From: backwoods upstate ny
fwiw, i prefer the 4-wire heated o2 sensor as used 94-04 vette (upstream sensor) as it has a dedicated ground wire for the sensor element...the matching connector can be found in the j-y on zillions of 3.1 GM v-6's, such as 94-96 corsica, etc and is up high just behind the alternator, easily "canned", usually not too dirty...if really on a tight budget ( a new sensor is abt $50 at napa) the 4-wire o2 sensor from those (same as vette 94-04) will often unscrew "cold" (you will need a "slotted" 7/8'' o2 sensor socket to get past the exh manifold heat shields readily),look on top center of rear exhuast manifold, also accessible without crawling under the car....tan wire (term A on connector) and purple (term B) connect to ecm (wire colors match typically) input and sensor "low"(ground), black wire (term C) to engine ground, pink wire (term D) to 12v ''hot in run only"
Last edited by redrose; Feb 13, 2008 at 08:53 PM.
Thread Starter
Team Owner
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From: sw Ohio
As for the 4 wire sensor, I dont see what the difference is, I mean they do the same thing as a 3 wire (heated). I have to crawl underneath the car anyway since I have headers the sensor is at the end of the collector.
Team Owner
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From: Athens AL
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One provides a constant heat source to the sensor element.
Melting Slicks
Joined: Feb 2006
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From: backwoods upstate ny
reference previously made to "crawling under" was only directed to acquiring the 4-wire connector and/or sensor from a "donor" vehicle, sorry if that was not clear.
