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Discussion Starter · #1 ·
To keep it somewhat short, I accidentally purchased a 92 jdm wiring harness when looking to replace my hacked-up harness. The problem now is that the harness does not have a plug for the rear o2 sensor next to the injectors. I found another thread where someone just took the signal wire from the front o2 sensor and ran a separate wire into the ecu where it would originally be looking for the other o2 signal. This seems pretty straightforward forward but I have no idea what pin I would run the wire to on the ecu or exactly how this process would work.

Or, if there is an easier way to wire around my missing rear bank o2 sensor let me know. Thank you in advance.
 

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It looks like that would probably work fine, but it would be wise to move the sensor to the downpipe somewhere after the two banks merge so you've got an accurate AFR reading of the whole engine, not just one bank.

You can find ECU pinouts here:

Go through and find out which connector you have. You likely won't have a wire in that pin of your harness so you'll need to add one.
 

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Discussion Starter · #3 ·
It looks like that would probably work fine, but it would be wise to move the sensor to the downpipe somewhere after the two banks merge so you've got an accurate AFR reading of the whole engine, not just one bank.

You can find ECU pinouts here:

Go through and find out which connector you have. You likely won't have a wire in that pin of your harness so you'll need to add one.
So I found that pin 56 shows that it is the “heated o2 sensor rear bank” so I would just be adding a wire from the front o2 sensor signal wire to pin 56 on the ecu?
Also, for your recommendation, I assumed the rear o2 sensor needed to be in the turbo downpipe so it has a similar reading to the front bank. Wouldn’t it have a different reading if it was further down the exhaust after they merge?
Thank you for the link and response.
 

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Yeah, I guess. It'll either work or it won't.

You're not actually wiring in a second sensor though, right? Just feeding the output from one sensor to two ECU inputs.

So, in my opinion, you're better off to have the single sensor fitted after the merge so the ECU trims fuel to suit the whole engine, not just one bank. The readings are the same anywhere in the exhaust, unless you've got precats or a main cat.
 

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92 harness would have the rear O2 connector at the fuel rail (right bank fuel rail)
The front O2 would connect at the top alternator bracket for reference placement
The rear O2 (left bank) wire would be about 2 foot in length so it can reach the fuel rail to connect into the harness
The front 02 (right bank) would have a shorter length wire connecting just above the alternator

With both O2 sensors going into the down pipe

This needs to communicate with the ECU
MAF related to what the O2s are seeing to

Instead of having one bank running healthy and the other bank getting drowned with fuel

Running wideband futher down in the collector pipe 5 to 6 inches back from where both of your down pipes collect to read both banks
 

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Wideband placement is important to the angle of which the sensor end needs to point at a downwards angle inside the exhaust pipe
For contaminants purposes
Cold starts / intake cleaners / seafoam etc...

Welded in bungs / most aftermarket exhaust already have these installed with a plug bolt
 

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Discussion Starter · #8 ·
92 harness would have the rear O2 connector at the fuel rail (right bank fuel rail)
The front O2 would connect at the top alternator bracket for reference placement
The rear O2 (left bank) wire would be about 2 foot in length so it can reach the fuel rail to connect into the harness
The front 02 (right bank) would have a shorter length wire connecting just above the alternator

With both O2 sensors going into the down pipe

This needs to communicate with the ECU
MAF related to what the O2s are seeing to

Instead of having one bank running healthy and the other bank getting drowned with fuel

Running wideband futher down in the collector pipe 5 to 6 inches back from where both of your down pipes collect to read both banks
Yes I understand where the o2 sensors should plug in, but the wiring harness I purchased was from a 92' JDM engine which only uses one o2 sensor further down the exhaust. This means I have the connection near the alternator for the front bank o2 sensor but the rear sensor connection near the injectors/fuel rail is not there.
That is why I have come here trying to find another alternative rather than purchasing a new wiring harness just for the rear o2 sensor plug. (spending $150-$200 for one missing connection)
 
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