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Rear O2 Sensor Issue


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Hi guys,

I seem to have come across an issue. Ive tried doing a search on this forum as well googling it but everything seems to come up unrelated.

I have a 07 LX470 grande. Ive always felt the car was quite heavy and underpowered at only 230hp, so about 4 months ago i installed an ITG performance filter, got rid of the heavy mid muffler and replaced it with a 18in magnaflow performance muffler and chopped off the rear hotdog type muffler so in effect the exhaust ends just before the rear wheels.

About 2 days ago i decided that i need more power, more go and because there arent many off the shelf performance parts readily available everything needs to be custom made, so i decided to get some performance headers made. I also got rid of the muffler like cats and replaced them with custom decat pipes that connect to the stock catback exhaust

Now heres the problem, there are two O2 sensors for each bank, pre and post cat. Because there are no longer any cats, the 2 rear O2 sensors have been disconnected and now the car has thrown itself into limp mode. The CEL, VSC TRC and VSC lights have all lit up and i seem to have lost my fuel economy.

I hear that the 2 pre O2 sensors are the important ones that help determine A/F ratios and that the 2 post O2 sensors are only for emissions control and to tell the ECU if the cats are working properly.

So the question is, does the ecu need the rear O2 sensors in conjunction with the front 2 to help run the car at optimum performance? Do i need the 2 rear O2 sensors or is there a way to just discard of them i.e disconnect them or something similar.

Thanks in advance for any help or suggestions you can throw my way. It will be greatly appreciated


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