Hey yall, I need to replace my Oxygen sensors, I'm getting the Bosch Oxygen sensors on Amazon, And Im wondering how much I need, And if I need to get different sensors for Upstream and downstream, Thank you.

 

If you’re not getting fault codes for the downstream sensors I wouldn’t bother changing them. They don’t give the ECU any feedback for modifying fuel. They only monitor the Cats to see that there is a difference between upstream and downstream sensors.

 

Part numbers are different upstream & downstream. I installed these 5 years ago:
You need two of each.

 

IMO, just replace all 4 of them and be done with it. Bosch units work best for me.

 

Harv... I wanted to ask if the Oxygen sensors are involved with calibrating fuel trim? How would the ECU do that without those sensors?

 

The front sensors are used for fuel trim. As said, the rear sensors are only used to monitor performance of the cats.

 

There are two different sensors, upstream (before the catalytic converter) and down stream (after the cat). The upstream sensors are used to monitor the exhaust and correct fuel trim levels based upon the presence, or lack thereof, of oxygen in the exhaust. The downstream sensors do nothing but monitor if the catalytic converters are functioning- they provide no feedback to the engine at all and are in place exclusively for emissions regulations. In some markets they didn't even fit rear sensors. A good running engine with a catalytic converter should have basically no oxygen in the exhaust after the cat, if there is, the catalytic converter isn't working and a check engine code is thrown.

 

Two excellent replies. thanks to both of you. I am poised to buy the Nanocom "Evolution" for my 2006 LR3 (and to share with other LR owners I am coming across in southern Manitoba)... but I am wanting to make sure I wind up with a scanner that can read fuel trims. Have just started corresponding with the Nanocom office to answer that question. (The "Evolution", since it is not VIN-locked, seems to be my best option.... IF fuel trims can be displayed.)

 

I don’t know the LR3, but I highly recommend the Nano Evolution for the D2 and P38.

 

Does it show you fuel trims for your D2? (A friend of mine wants me to purchase an older Snap-On scanner with an LR card... but I expect that would be cumbersome. And underwhelming. It would never be able to tackle a dash cluster change, as the Evolution can.)