O2 Issues and confusion in general
 

I purchased a new O2 sensor for my 85 RoW. As you can see from the pics below, it has a cat and O2. However, my O2 only has 1 wire instead of the 3 that are on the one I purchased. I am assuming since it is a RoW vehicle the cat and O2 was added when brought to US in 85. Is my O2 from an older car? Any idea what year so I can exchange the one I bought? In photo 2, should that empty wire be plugged in above my O2 plug in photo 3? It looks like it fits but I can't see it reaching that far. I am so confused????

http://forums.pelicanparts.com/uploa...1115213829.jpg


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Any ID stamped on the current, one wire sensor? Did it work correctly at some point?

Unfortunately I didn't pull it last night since I knew I couldn't replace it and it is my daily driver. I will pull it tonight and then put it back in. Ideas on the uplugged wires?

K, first, below are the Bosch part #s for a US '85 Carrera. Does your new one match either of these?

Do you have a Euro or US ECU?

I can check the wiring tonite if someone doesn't chime in with the correct setup info.

http://forums.pelicanparts.com/uploa...1115215171.jpg

Looks like my suspicion was correct. The sensor in my car is a one wire Bosch 258 001 047 which matches an 83 SC. Nice part is that the cost is about 1/3 as much. Anyone have any idea on the what the extra plugs are for? could it be that the extras are for the additional two wires that are supposed to be on this year?

The oxygen sensors on the SC work as merely a additional enrichment device for emissions control. the one wire provides a small voltage to the control unit, which in turn controls a valve that gives the motor a little more fuel.

On the later Carreras with motronic fuel injection, the sensor controls the overall mixture of the fuel injection. I'm pretty sure it works like this..

One wire is to heat up the O2 sensor (as they dont usually provide accuracy until they have heated up), one wire is a small voltage from the DME to the sensor, and the other wire is the signal output from the sensor back to the DME. They usually work that way..

The nice thing is that you can get a universal Bosch 3 wire sensor for like $25 or so at the local Pep Boys. The catch is that you'll need to cut the connector off the old O2 sensor and solder it on to the new o2 sensor.

I think Jared is correct in his description of the wire functions. You can use a generic but you'll need the correct 3 wire type connector to hook it up correctly. I don't know if the O2 sensor with 1 wire is even working on you car and actually doing anything. It may be causing some of the AFM problems from your other thread. Not positive just a question I'd be asking myself. Maybe someone more knowledgable will chime in here.

Dan - That was my next question. You beat me to it. That begs to ask again, what are the wires that are not connected?

THey could have added an SC cat, the pics looks like the cat in my car, however i think they were the same for Carrera and SC models.

I'm thinking that maybe the early motronic systems used a one wire, and you simply had the wrong O2 sensor on there in the first place.

Can anyone confirm if the early Carreras had a one wire?

Rick - How do I know if I have a Euro or US ECU?

The open plug in photo 3 goes up to what I guess is the ECU. Still confused. Logic would tell me that a 3 wire O2 should be put in and wires 2 and 3 should be plugged in to the spare socket above the O2 sensor plug. Not sure how I would match wires though. Thoughts?

Jared - In pulling up the part number for the sensor, 83 had a one wire and 84 on had a 3 wire.

3-wire universal sensors have a single signal wire, the ground reference is via the threads and mounting point. The other two wires should be the same color and are for the heater, no polarity.

On the universals I've bought, the signal is white and the heater pair is black.

Lad,

I suspect the SC / Carrera Cat are the same.

Under the driver seat you will find the ECU. This link may help you determine what you have---> http://members.rennlist.com/messinwith911s/DMEHacking.htm

Hopefully. JWW, SteveW, Loren or others will chime in.

Charlie - Are you saying that the two blacks would not run to the motor but would actually be supplied with voltage from elsewhere? Perhaps the plug in photo 1 that is not connected?

Then there is no difference in the Carrera models. they all had three wires.

84 was the first year

The 3 Wire O2 sensor is a Heated sensor. It gets 12 V for heating after you turn the ignition.
I allows the sensor to get up to operational temperature faster. The one wire sensor is not, It will only start sending signals after the car is warmed up.
They are both narrow band sensors which send a voltage between 0-1.05 volts to the DME, signaling rich or lean conditions, The DME alters the mixture to compensate.
I'm not familiar about ROW cars, but my 1986 US spec, has the same CAT with a 3 wire sensor. The plug is round, not square as your picture shows. My connector is found near the fuel filter as well. ROW cars did not have cats in the first place, so you may need to get a hold of the wiring diagram for O2 sensor, before you plug anything anywhere. I would be concerned about my DME.

Hope this helps!,

I have a '79 RoW (no OXS) so I'm not familiar with the connections in the photos, but PorscheG gave a good description of what the heater is about. I would think the heater power is on a timed relay that shuts off about 60-120 seconds after startup since the heater is supposed to get things up to temp in 30-60 seconds.

The Bosch site navigation is sort of ugly and makes you follow gobs of links but eventually you can find good info on the sensors. I was just using it a few weeks ago to look into extra WB sensors for my LM1 and they seemed to have a lot of info.

The ECU on my car is RoW based on Rick's DME hacking link.

Did a RoW model car come with an O2 sensor? If not, how did the system compensate for not having that information?

I was replacing the sensors for my '91 200tq ECUs. My SC doesn't have a sensor or cat, just plain old earlier K-jetronic w/ the metering plate to measure air and no feedback loop or electronics.

Is it possible on my RoW that prior to the O2 being installed that the wire in photo 2 and 3 were plugged into each other? Would the ECU or DME control the fuel mixture when a O2 is not present? Really need someone with a RoW model to chime in. I have no emission requirements here in Utah so bypassing the sensor is an option.