I bought 2 upstream ones from AMZN. One failed right out of the box. You also need to check the wiring harnesses themselves. I think someone had to do a repair on mine before I owned the car. Bosch 15175 are currently $55.19 on AMZN.

 

I run an OBD Scan, please let me know what O2 sensor need replacement and where exactly they are located if possible. I got 5 faults read on scanner

1) O2 Sensor Bank 1 Sensor 1
2) Evaporative Emission System Leak Detected (Large Leak)
3) System Too Lean Bank 1
4) Oxygen Sensor Too Lean Faults Bank A and B
5) Cylinder 2 Misfire Detected

Please help me determine which part and where.
Thanks

 

O2 sensor bank 1 is drivers side pre-cat sensor.
one thing to remember, an intake leak(or exhaust leak for that matter) can cause the other codes.
I would first key on getting all intake leaks taken care of, the Evaporative system leak could easily be causing it to run lean.

 

Thank you all!

 

Let us know, how it going once you figure things out.
When I got mine, there were 9 codes, MIL on, 3 amigos off and on.
I took them one at a time and the vacuum leaks cleared several, new plugs, wires and coil cleared my misfires, new knock sensor cleared that one. All new O2 sensors finished the rest, except the passenger's side cat(misfires killed the cat). Got a code eliminator(basically an extension for the O2 sensor) and the cat code was gone. Truck passed inspection and has been code free every since.
ABS (option B) took care of the intermittent Amigos.

 

Thank you. I got all the sensors from amazon and an MAF sensor as well. Both my discos failed the nj inspections. But I'll let one pass for the mean time. In the list of failed codes from dmv includes a maf code. I would rather change it too. Right? I kept all suggestions in the forum and troubleshoot them one by one if I could. Thanks

 

What causes O2 sensors to fail?? DO I need to check other things like the Mass Air Flow Sensor? do they function on their own and so its only the wiring to them or the sensors themselves??
Thanks guys and heres my updated code readings on them..
I just want to be sure I don't pay premium price for them if the OEM ones will fail because something else is going on...

 

O2 sensors do make their own voltage, but they need to get hot to do so. If you have readings that look like dead sensors or codes for low or no activity, try forcing the sensors rich. Take off a vacuum line and spray some crab cleaner, brake cleaner, or propane in it with the engine running. Watch the live data and see if the voltage starts climbing on the sensors. If it does, you may have a vacuum or exhaust leak.
If that doesn't work, there may be a problem with the heater circuit for the sensors.

 

I'm encountering a similar fault code with new O2's from Atlantic British; the heater circuits are cycling on and off on about a two second interval even though the engine is running around 194 degrees - I recently switched to the lower temp gray LR thermostat and now am wondering if engine is operating at the temp that confuses the heat circuit setup or if my ECU has developed a glitch.

 

I second this opinion. I ended up buying the Bosch upstream ones from a store because I needed them in a pinch to pass emisisons, but later checked and saw these prices on Amazon. Buying my downstream ones soon, gotta love Prime.