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Just replaced Bank 2 sensor 1 because of no reading. Well new sensor worked well for 10 miles then bam! Live data was showing the sensor jumping like it should when first installed then went to.000.

So now.... I start the vehicle cold and have .445 once the vehicle warms up the Voltage starts to drop slowly until it reaches .000. I am also showing a open loop on fuel system 2.

I know my sensor is compensating for a lean mixture on bank 2 and just falls all the way to .000. What do I need to start doing now? No other codes yet!:dunno:
 

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Discussion Starter #2
Does not seem to run bad just rich. No vaccume leaks found. Looking now on how to pull the injectors and clean them. Not sure what road to take.
 

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Leave the injectors along, as they say, "If it ain't broken, don't fix it".
They are not causing you to run rich.
A number of years ago, Rover released a TSB on 02 wire harness and connection issues, you might want to try and find it.
Any way a can of 44K will do a lot better cleaning the 02's, if it were needed.
 

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You have more troubleshooting to do. You are correct the 02 sensor is not the issue. The 02 voltage should drop off to 0.00v after failing to achive closed loop operation (the sensor is still working, the computer is ignoring it because fuel trim values are too far out for it to compenstate for). At this point you should look at your Long Term and Short Term Fuel trims on each bank. See if the combined total of Bank 2 STFT + LTFT is a positive or negative number. This will tell us if it is a Rich or Lean condition and if you should continue to look for a vacume leak or move on to something else like the injector.

Did you initally have a misfire code. if so what cylinder (s). This will help narrow it down also.

There are a number of things that can cause 02's into reading extream values. Vacume leaks, poor spark, bad injector (leaking / clogged), open air leaks in secondary air injection, upstream exaust leaks, sticky or burnt valves, worn camshaft... etc.

What year is the truck and miles, w/ or w/o secondary air.
 

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You say it was working fine for 10 minutes? Bad sensor?

It running rich could be due to the sensor reading 0, not the sensor reading 0 due to rich (which it wouldn't read 0 when rich, but would both read low and smell rich if it were an ignition misfire, or lack of compression, etc)

Before you tear into it too much, I would suggest checking the sensor connection, and maybe swap side to side, make sure it doesn't follow the sensor.
 

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Discussion Starter #6
Here is a snapshot of the live data that show trim levels. Let me try to figure the math out and get an answer...:dunno:
No air leaks that I can find with starter fluid. There is no oil on harness or the sensor plug itself. No misfire codes or any other codes I can find. The truck runs ok. Maybe just a slight idle shake but nothing too noticable.
 

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From those readings everything looks okay. You have a Bank 2 LTFT of +25 and a STFT of -25. That’s a total of 0 which is what you want. Something caused the FT to max out in the positive direction. A positive fuel trim reading is due to the O2 detecting too much oxygen at the sensor and the system adding fuel to compensate. Excess oxygen is usually due to vacuum leaks or insufficient combustion.

In a normal situation LTFT will be a number less than +/-10 and STFT will constantly cycle +/- 10 to offset the LTFT to maintain a target of 0. If STFT is operating at a value greater than +/-10 it starts adding or subtracting to the LTFT to keep STFT within +/- 10. I believe +/- 25 is the MAX adjustment of Fuel Trim the ECU will compensate for.

Are these readings at full operating temp? You can disregard any O2 readings at less than full operating temp. Since you can see live data with your meter you should also compare readings at idle and 3K+ rpms. The ECU will cycle in and out of closed loop operation until a stable closed loop can be achieved.

As an example I had a Disco II with perfect readings at Idle. At 3K rpm the STFT + LTFT was +25. This turned out to be a worn camshaft. Only at 3500 RPM would it misfire. Creep around and you would never know there was an issue.

My suggestion sense you just put on a new sensor is to drive it for several cycles to see if the LTFT comes back down to a value less than 10 or if you get some type of code. Without referencing the manual it seems like 12-20 cycles is required to clean up the previous events, short of resetting the adaptations. If the system fails to achieve and maintain closed loop you will eventually get a code.

More info for you.
Land Rover Workshop Manuals - Discovery II - Exhaust Emission Control Operation
Land Rover Workshop Manuals - Discovery II -
Land Rover Workshop Manuals - Discovery II -
 
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