The Camaro Club (UK)

Does anyone know where the o2 sensor should go? I will need to add one at some point (once the camaro is done). The wire is on the pass side,so guessing it's a) not in the manifold (have stock manifolds and no place for it there) and b) somewhere before / after the Y join? I've tried searching and came across some pictures that were so badly taken (likely because of an odd location) that i couldn't make out where exactly in the system the sensor was / is supposed to be. Cheers!

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Changed mine Yesterday!

Drivers side manifold. Pointing towards the front of the car. Single wire runs under the manifold to a connector just under the alternator, by the power steering pump on mine. 22mm long reach socket needed, much easier to access without air antismog lines fitted.

I can take a picture of mine tomorrow if you want?

I did discover the 2nd one on mine (under the car) wasn't connected. No idea why someone put it there......

Thank you!

Yes, that will be very helpful thanks! Sounds like an awkward place.. will need to weld in a bung so sounds like it won't be a fun job. Strange that i have a wire on the pass side engine bay, will need to trace this back! I wonder if the second wire you mention you have that is unplugged is the one that sits after / before the cat?

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The upstream O2 is used by the computer to adjust the air/fuel ratio, the downstream sensor (after the catalytic convertor) is to make sure the cat is working properly.

Took a picture of mine tonight.



The arrows point to the O2 sensor and where the connector is (under the alternator, behind the power steering pump). You can see the single wire running between the two.

As you can see I have the standard log headers as well, the O2 bung is in the front of the drivers side header, before the connector to the rest of the exhaust.

To my knowledge (and the dealer manual I have) the third gens only ever ran one O2 sensor, in this location. The second sensor run on the fourth gen would have been behind the cat, but was never run on the third gens as far as I know. Mine was retrofitted for some reason by a previous owner and was connected to a stand alone box. Yours shouldn't have this (and nor should mine really!!).

Not sure what year yours is, mine is a 1991. It's possible your O2 sensor is on the other side if it's an earlier model, but it should still be in the header.

Hope this helps!

Thanks Jon!

That's perfect, very clear and easy to see. Most pictures are close up from an obscure angle, so this puts it nicely into perspective Mine is an '87 and the alternator is actually on the passenger side, but by the sounds of it the upstream sensor does need to be on the drivers side. I'll have to remove the AIR stuff (still on the list, so close to getting the Camaro done) so then i should be able to find a good place for the bung in that area that will allow me to weld and drill it in.... should be fun

I wonder why they retrofit a cat based o2 sensor on yours, maybe that box it plugs into is a simple system to bring up a warning light if the cat does malfunction?
Thanks for the explanation Neil. It definitely needs the a/f ratio adjusted as it always runs rich (smells lovely) due to no sensor connected so once it's connected upstream, sounds like it will help

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Well well well, the story takes a twist. Yesterday i had a quick check under the hood to make sure the levels were ok etc. and i thought i would have another look at the wiring as i was sure i had a disconnected wire on the passenger side. I saw the disconnected wire that looks exactly like the O2 sensor plug, so i tried to follow it across to the drivers side to see if it had been pulled across. And there, under LED light, through the mess of the AIR system, i saw that there was an 02 sensor hidden away and plugged into the stock manifold and plugged in! So, it turns out then that i do have an o2 sensor and it is plugged in. I will change the 02 sensor out as i'm sure it's not good any longer.

The only thing left to figure out is about the other side. It has a connector for what looks like the post-cat sensor (which isn't present due to the exhaust being aftermarket). The connector has the same colour wire and the same connector type as the drivers side. I'm trying to work out what it means to the ECU to not have a signal from the cat sensor. Should i add one in? I have an o2 threaded bung i can weld in. But, not sure if that will do anything, seeing as it doesn't have a cat, would it still misread anyway, making it pointless to add in?

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How to post pics: When writing a message, scroll down and use the "attach file" option. Where possible, a photo sharing service can be used such as Flickr, Imgur etc. The image location (usually ending in .jpg) can be copy and pasted between the ][ brackets that appear when you click the 'Img' button (you can find this button at the top of the message box).

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I'm 99.9% sure no third gens every had post cat O2 sensors fitted. As the computer is early (ODB-1, not 2) they are very basic and as such can't check if things are working correctly, only if they are working at all.

The fourth gen had post cat sensors, but had more updated management systems with monitoring included (ODB-2) so it could determine that the cat was working properly and adjust things for the optimum running.

I don't think there is any benefit to adding a post cat sensor as the computer can't use the info provided. Although mine had one welded into my aftermarket exhaust it was connected to a separate box, which then wasn't connected to anything so I have no idea what it was supposed to do and as such is now removed!

I have an original Chevy dealer manual for my car (though it is a 1991 model so could be a bit different to yours) with the wiring diagrams etc. I can have a look in there if you can send me more info (photo of connector / wire colour / exact location etc) and let you know what it says it's for if you want? Let me know!

The purpose of the downstream O2 sensor is simply to make sure the cat was working. If the output voltage stays steady around 0.5 volts with no major fluctuations the computer considers that the cat is working properly and does nothing. If the voltage matches the front O2 sensor and swings rapidly from 0.1 to 0.9 volts, it sets a trouble code and turns the MIL light on.
2 high value resistors set as a voltage divider to give 0.5 volts can fool it very easily

Thanks for the helpful advice as always! I've had a hell of a weekend on the camaro (more wiring fun) so i'm just catching up on the messages. I'll take a pic today of the passenger side sensor. Good to know that i can do without it if there is a post cat one. I definitely want to sort the front sensor out as it's burning rich. I've put together a small shopping basket of service parts at rockauto, but the shipping cost matches the parts cost, so hopefully can fit it all into a suitcase in a month or so when i visit the land of the free.

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How to post pics: When writing a message, scroll down and use the "attach file" option. Where possible, a photo sharing service can be used such as Flickr, Imgur etc. The image location (usually ending in .jpg) can be copy and pasted between the ][ brackets that appear when you click the 'Img' button (you can find this button at the top of the message box).

How to post youtube vids: Click on the 'youtubeHD' button at the top of the message box and in the middle of the ][ brackets that just appeared, copy and paste everything from the youtube web address that appears after the = sign i.e if this is the url: https://www.youtube.com/watch?v=K2cNqaPSHv0 just copy "K2cNqaPSHv0").