Using signals from Bank 2 to Bank 1 side

In see this asked on different forums but the responses vary. Technically if you had an exhaust manifold leak on the Bank 1 side of an OBD2 V8 and the corresponding upstream/downstream sensors code lean condition could the signal wire(s) from the Bank2 side operating at proper range be split and also feed the Bank1 side at the same time?

Not saying I would do it and that it won't correct the real problem...just something that I always wondered about.

Not likely. The engine will generally tune itself either rich or lean against the fuel trim limits when you accidentally swap the sensor wiring left for right. Sometimes, one side goes rich and the other goes lean. I can't see a single bank reading the wrong O2 sensor working any better.

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Originally Posted by lionelhutz

Not likely. The engine will generally tune itself either rich or lean against the fuel trim limits when you accidentally swap the sensor wiring left for right. Sometimes, one side goes rich and the other goes lean. I can't see a single bank reading the wrong O2 sensor working any better.

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Thanks I understand what you are saying..I was just wondering if the pcm would accept the (split) sensor value or would the value change (resistance wise) since it is being split and sent in two different locations? Not sure from reading the tuner forum posts but it appears that some tuner folks are removing OEM exhaust manifolds with two upstream O2 sensors and installing headers with only one O2 sensor...I was just trying to understand if it's possible. Guess this is more of an electrical question. Thanks again.

I'd believe an exhaust sample from both banks might work. A challenge may show up if the signal is too far from stoich. If the pcm corrects fuel but doesn't see the O2 return to normal it could continue to make larger and larger corrections until the engine runs poorly.

Your question is slightly different in that you're asking if one sensor signal can be used for two inputs. That is generally not the best approach. The ECM/PCM applies voltage to the O2 sensor. As the sensor warms it applies greater voltage to the signal line. The PCM monitors voltage on the line and sets codes if it's outside the limits. Voltage supplied from two sources when can cause false codes or can change pcm response to a problem. Additionally as the sensor produces current to be delivered to two sources, the voltage at both inputs will be lower than when only one is used. Again, the result is expected to be an incorrect signal. Better IMO to try and find a way in the calibration to use a single sensor or to add an O2 bung to the header on the other bank.

However, there are plenty of people who will skip all the right and wrong approaches, tie two sensor signal wires to one sensor, and drive around. Those people will have more practical advice about what actually works based on experience. OEM engineering can be quite robust.

Thanks guys here are a couple of related link discussions that got me started:

https://www.spyderchat.com/forums/sh...ed-both-Inputs

5 wire:

http://greenhulk.net/forums/showthread.php?t=216128

First post describes hombrew effort using NB sensor. Not a preferred solution imho.

Second post decribes microprocessor based solution for WB output. This orange is definitely not from the same apple orchard as the first.

In the first link there is a poster that posts how to do it, followed by another poster saying it doesn't work and then the poster who posted how to do it responds that it doesn't work...

The second link is a circuit to split a wideband signal.

Neither of those links is about a V8 with split exhaust.

Based on your question of a V8 with split banks - it would never work. Bank 1 and bank 2 fuel trim independently of each other. So, there is no way that bank 1 would fuel trim properly when reading the O2 from bank 2.

Now, you're just asking about splitting a O2 sensor. It would likely work fine signal wise. The level might drop a little bit, but the PCM is just looking for the narrowband O2 to switch back and forth around 0.45V so slightly less signal wouldn't make much difference as to what the feedback represents or how the PCM uses it.

Now, keeping the PCM happy with the fuel trims or fault codes is another story.

Thanks...I have no plans on doing it...just something that I couldn't get in my head. You are correct one guy says how it works, then another says it doesn't then they all go off on tangents...that's why I made this post. Probably would have been a better to just ask if the ecm/pcm would not drop dtc's if both upstream and downstream sensors (all 4) were installed in one manifold side.