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O2 sensor wiring

Explodemylifepls

Well-Known Member
Joined
September 27, 2021
Messages
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City, State
Kansas
Year, Model & Trim Level
1997 explorer xxl
Hello, my 1997 explorer 5.0 is still not running right. Lean on bank 1 code but it is not lean it is very rich, smells rich and when I went to replace the o2 sensors they were caked in soot. So now my question and only question is where do the o2 sensor wires go? Through the bus connector at the bell housing and then do they go right to the ECM?? Reason I ask is I thought instead of pulling the trans out and looking over the wiring harness I could make a harness that goes from under the truck connected to the o2 sensors up to the ecm or wherever they feed. I replaced the sensors, no change, it's throwing a lean code with low inconsistent voltage but it's very clearly rich. I feel I may have squished the harness in between the block and bellhousing when I did the rear main and damaged the wires, I don't know why else I would have this erratic issue. It's only on bank 1. I get 10-11 mpg so don't really drive it much because of that.
 






What is the code

If an 02 sensor is reading lean the computer will add fuel in an effort to correct it, which can feel/smell rich

The 02 sensor wires go directly to pcm for the most part yes


On the 5.0 three 02 sensor plugs are on top of the transmission and can be accessed through the floor panel under the center console. The front drivers side sensor is wired along the back of the engine drivers side

If you pinched the wiring harness it would be pretty obvious as it is about 1.5” in diameter all three 02 sensors and all transmission wires in the same loom

Post up your code, it sounds to me like the 02 sensor is doing g it’s job and you likely just need to fix the reason it’s reading lean
 






P0171 and P1130. The P1130 is new and only came up after swapping o2 sensors. The 0171 has been there a while. I spent a couple hours with a smoke machine a while ago and fixed a lot of vacuum leaks and got it drivable but it still will average 11 mpg driving conservatively with 31s which is not right.

The downstream o2 sensors read pretty close to each other but the upstream sensors and voltages are not close to each other. It has new EGR components also and does not throw the egr codes but still threw a lean code when the egr was blocked off. It may have a small exhaust leak on the right side but barely noticeable. It feels like it keeps adding fuel into the trim but still cannot get it right.

I have not tried pulling the center console yet and it doesn't really make sense to me that I could squish the harness and only cause an issue with one circuit, but the new code appearing after swapping sensors is strange. The new ones are Bosch and the old ones were denso iirc.

It's mostly my spare vehicle as it's a little beat but I like to drive it occasional and only 220~ miles of range on a 20 gallon tank is no fun and not very practical for the "intended purpose"
IMG_2756.jpeg
 






Inspect the little pins in the wiring connector going to the 02 sensors

Also make sure you did not swap some sensor around d the three on the passenger side all plug in right next to each other it is easy to accidentally plug the upstream sensor into the downstream plug… they are color coordinated
 






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