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2005 Outback 2.5i - 5 speed - 191K
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Discussion Starter · #1 ·
I got RomRaider going and came across some questions.

It allows me to log the REAR O2 sensor however the front O2 sensor is not even an option.

Can anyone with a 2005 2.5 take a photo of the available parameters in RomRaider?

I attached a photo of the RomRaider screen for reference.

Also, there is a video of the O2 Sensor reading. It is all over the map. 0.1 - 0.8.

https://youtu.be/6wsbHjVJbLA
 

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All good.

"A/F Sensor #1" is the front O2 sensor (i.e., the wide band O2 sensor before the cat) with readout selection AFR or Lambda.

In regard to the rear O2 sensor, the video only shows the voltage changing, but not what is happening as far as engine operation. The Rear O2 Sensor voltage can vary between 0 and 1, depending on the current engine operating/driving conditions. For example, on a cold start, it might be down around 0.1 V or varying fairly rapidly between that and 0.8 V or so. When the cat reaches its operating temperature and is functioning properly, and the engine is idling or during steady throttle cruising, the voltage will usually be between 0.6 and 0.9 V. When the accelerator pedal is released while driving at roadway speeds, the fuel control system cuts injector fuel delivery, and the voltage will drop to 0 or 0.1. (At the same time, the A/F Sensor #1 data will also respond to the fuel cut -- AFR will go to 20:1, or Lambda, which is normally at 1.0, will rise to about 1.4.)

Incidentally, what's the ECU ID number at the lower right of the screen? Also, does the CAL ID have a number?
 

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Discussion Starter · #3 ·
All good.

"A/F Sensor #1" is the front O2 sensor (i.e., the wide band O2 sensor before the cat) with readout selection AFR or Lambda.

In regard to the rear O2 sensor, the video only shows the voltage changing, but not what is happening as far as engine operation. The Rear O2 Sensor voltage can vary between 0 and 1, depending on the current engine operating/driving conditions. For example, on a cold start, it might be down around 0.1 V or varying fairly rapidly between that and 0.8 V or so. When the cat reaches its operating temperature and is functioning properly, and the engine is idling or during steady throttle cruising, the voltage will usually be between 0.6 and 0.9 V. When the accelerator pedal is released while driving at roadway speeds, the fuel control system cuts injector fuel delivery, and the voltage will drop to 0 or 0.1. (At the same time, the A/F Sensor #1 data will also respond to the fuel cut -- AFR will go to 20:1, or Lambda, which is normally at 1.0, will rise to about 1.4.)

Incidentally, what's the ECU ID number at the lower right of the screen? Also, does the CAL ID have a number?
THANK YOU

I have the car at running temp and at idle

Temp 185 Degrees +/-

A/F Sensor 1 is reading "Lambda" and is steady at ~.97 - 1.03
A/F Sensor 1 is reading -0.12 - +0.12 mA
A/F Sensor is reading. 31Ohms

Rear O2 Sensor is again bouncing between 0.06 -. 86

ECU ID: 2F120A4206
CAL ID: UNKNOWN

Info I have read suggests the rear sensor should fluctuate slowly and should remain around 0.5 (+/- 0.2)

My rear O2 is ALL OVER the place.

Also read the front O2 is supposed to fluctuate more, going from lean to rich. Mine does not appear to fluctuate. Attached video shows all A/F Sensor 1 readings available.

Sent 2nd video w readings at ~2500 rooms for about 30 seconds.

Any other readings I should watch?

https://youtu.be/E27oL8tCDsk

https://youtu.be/a4oQ3qMWWX4
 

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THANK YOU

I have the car at running temp and at idle

Temp 185 Degrees +/-

A/F Sensor 1 is reading "Lambda" and is steady at ~.97 - 1.03
I'm catching up a bit on this myself. There should be a fluctuation on the front sensor reading, but it may be a question of scale- in other words it looks like a flat line if you're zoomed out too far. Seeing the voltage on a scope is useful for comparison to the other sensor, but not particularly useful for other diagnostics.

On the other hand, reading it in lambda is much more useful for other things.

The bigger point is that lambda 1.00 is a critical threshold of perfect combustion. If you are seeing results on both above and below 1.00, then the ECU appears to be correcting, crossing, correcting and crossing the line just as it is generally supposed to.
 

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. . .There should be a fluctuation on the front sensor reading, but it may be a question of scale- in other words it looks like a flat line if you're zoomed out too far. Seeing the voltage on a scope is useful for comparison to the other sensor, but not particularly useful for other diagnostics.
Why should there be a fluctuation under steady state conditions, if "fluctuation" means constant high/low changes?

I raise this because it's my understanding that with the wide band A/F sensor, the system can operate in a more linear fashion, monitoring actual AFR and adjusting proportionally. This is because the wide-band can output a signal that's proportional to the variance between the ideal AFR and the measured exhaust AFR. Older O2 sensors could only indicate lean or rich, therefore requiring the ECM to constantly switch the fuel trim between lean and rich to determine when it's at the right point on average. It was this switching that resulted in the constant fluctuation of the output voltage of the pre-cat O2 sensor.

Here's a paper that might be of interest: http://www.partinfo.co.uk/files/4 Wire Wide Band Oxygen Sensors.pdf
 

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Why should there be a fluctuation under steady state conditions, if "fluctuation" means constant high/low changes?

I raise this because it's my understanding that with the wide band A/F sensor, the system can operate in a more linear fashion, monitoring actual AFR and adjusting proportionally. This is because the wide-band can output a signal that's proportional to the variance between the ideal AFR and the measured exhaust AFR. Older O2 sensors could only indicate lean or rich, therefore requiring the ECM to constantly switch the fuel trim between lean and rich to determine when it's at the right point on average. It was this switching that resulted in the constant fluctuation of the output voltage of the pre-cat O2 sensor.

Here's a paper that might be of interest: http://www.partinfo.co.uk/files/4 Wire Wide Band Oxygen Sensors.pdf
Appreciate the reading, thanks!
 

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THANK YOU

I have the car at running temp and at idle

Temp 185 Degrees +/-

A/F Sensor 1 is reading "Lambda" and is steady at ~.97 - 1.03
A/F Sensor 1 is reading -0.12 - +0.12 mA
A/F Sensor is reading. 31Ohms

Rear O2 Sensor is again bouncing between 0.06 -. 86
Shouldn't under steady state conditions. But just looking at that, in isolation (relative to other parameters), doesn't lead anywhere. That could happen even if the coolant temperature is at 185 F, but the outside temperature is very cold, and the cat is having difficulty lighting off.

I'd suggest additional parameters, and instead of videoing, use Romraider to log (record) the data and post the .csv file (needs to be "zipped" to attach to a post) here.

For starters, include:

Battery voltage
Engine Speed
Vehicle Speed
Accel. Opening Angle %
A/F sensor #1 AFR
A/F correction #1 %
A/F learning #1 %
A/F sensor #1 resistance
Rear 02 sensor #1 V
A/F Sensor #3% (32 bit)
Coolant temp (F or C)
Manifold absolute pressure (psi or kPa)
Mass airflow (g/sec)
Throttle opening angle %
Engine load (calculated) (g/rev)
Fuel injector #1 pulse width (ms)
Ignition total timing
Intake air temperature (same F or C as Coolant temp)
Knock correction advance
CPC valve duty ratio
Number of exh. gas, recirc steps

Also, under the Settings drop down menu, select "enable fast polling".

ECU ID: 2F120A4206
CAL ID: UNKNOWN
I'll see what I can find. But could you please confirm the ECU ID number. (Can't find 2F120A4206, but 2F120A4606 shows up in the Romraider Forum.) Also, is it a CA-spec emissions system, or FED?

Info I have read suggests the rear sensor should fluctuate slowly and should remain around 0.5 (+/- 0.2)

My rear O2 is ALL OVER the place.
If the system is working properly, it's my understanding that the rear O2 voltage should be fairly steady under steady-state operating conditions. In that I mean it would be fairly steady within the 0.6-0.9 V range and not fluctuating below 0.5 V.

Also read the front O2 is supposed to fluctuate more, going from lean to rich. Mine does not appear to fluctuate. Attached video shows all A/F Sensor 1 readings available.
As rasterman mentioned, it might be a question of scale. However, I'm not sure that we should actually expect to see fluctuations, and then conclude there's something amiss if it isn't fluctuating.

Perhaps subject to interpretation. See my above response to rasterman. I'm open to clarification.
 

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rather than looking at the "dashboard" tab, if you just go to the "graph" tab of RomRaider and pick those 2 parameters (rear o2 and front afr #1) then you should see the front AFR bouncing and the rear o2 flat-ish (or not). Click "combine" graphs.

Check out this graph from my California '05. These are my 3 rear o2s. The "fronts" are behind the 1st set of cats. So #2 fluctuates, just very little. My "front o2 sensor #1 and #2" is the same part number as your "rear o2" , I think.

Front O2 sensor #1 is what I believe to be bad (keep in mind this is actually a rear o2... it's behind the first cat)
Front O2 sensor #2 is what I believe to be correct/good (keep in mind this is actually a rear o2... it's behind the first cat)


Rear o2 I think is fine as well.
 

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Discussion Starter · #9 ·
I'll see what I can find. But could you please confirm the ECU ID number. (Can't find 2F120A4206, but 2F120A4606 shows up in the Romraider Forum.) Also, is it a CA-spec emissions system, or FED?
This is a FED vehicle. Only TWO O2 sensors on the vehicle. The ECU ID is correct (well....97% sure) but I will verify tomorrow. We are about to get 12" of snow and I am not going anywhere until tomorrow.

Shouldn't under steady state conditions. But just looking at that, in isolation (relative to other parameters), doesn't lead anywhere. That could happen even if the coolant temperature is at 185 F, but the outside temperature is very cold, and the cat is having difficulty lighting off.

I'd suggest additional parameters, and instead of videoing, use Romraider to log (record) the data and post the .csv file (needs to be "zipped" to attach to a post) here.
I will post the .csv file tomorrow, please stay tuned for that file. I will also add the parameters you mentioned.

Thank you for your patience. I will look forward to your thoughts.
 

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I will post the .csv file tomorrow, please stay tuned for that file. I will also add the parameters you mentioned.

Thank you for your patience. I will look forward to your thoughts.
Staying tuned to see a full parameter list....
 

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Discussion Starter · #11 ·
I'd suggest additional parameters, and instead of videoing, use Romraider to log (record) the data and post the .csv file (needs to be "zipped" to attach to a post) here.
To whet your whistle, I did make this log file today. It only has the limited parameters shown in the video but maybe it has some of the answers.
 

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To whet your whistle, I did make this log file today. It only has the limited parameters shown in the video but maybe it has some of the answers.
Figured out the uploading .csv files. This is only the few parameters logged from my earlier videos. Maybe it has some clues.
Limited info, but we can see/confirm some things in the data, graphed (attached).

Certainly, the rear O2 sensor voltage is fluctuating a lot, especially during the high rev period.

The A/F Sensor Lambda appears normal. Stable around 1, but we see it go to 1.4 when the rpm drops from 2500 to idle, presumably when the throttle is released and the fuel delivery is cut.

Also, at the time the rpm is dropping, the rear O2 sensor voltage drops close to zero. This isn't obvious in the stacked graph, but the second attachment (below) is an expansion of that time period, and the relationship between the presumed fuel cut and the two sensors is apparent. It looks as if the sensors are responding, but I'm suggesting a third log here to address this more rigorously.

In regard to logging, with the number of suggested parameters, the time between scans might be higher than in the current log which has about 100 ms between the lines in the .csv spreadsheet, but be sure Romraider Logger is set for fast polling.

Logs I'd suggest (all with the engine etc fully warmed up):

1) 1-2 minutes, straight idle -- no accelerator, A/C off, no turning lights or radio on or off etc.

2) 1-2 minutes, straight driving with minimum variation in throttle, etc, at around 40, or 50 or 55 mph, whatever you can maintain steady speed with little throttle change.

3) Drive at 50-60 mph for a minute or two, turn On Romraider logging, wait 10 seconds or so for the log to record the driving data, then instantly release the accelerator pedal (logging continuing). Let the car coast for 5-10 seconds (not more), then resume driving, and turn off the Logging. Repeat this a second time (so, two logs of this test).

Incidentally, is the car essentially stock, or are there any mods (engine, exhaust etc)? Are the exhaust and two sensor original, or replacements, and if the latter, make/model etc of the parts used, if you know.

Also, is the car up-to-date on all recalls, in particular, any relating to reprogramming of the ECM?
 

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Putting to paper some thoughts on post-cat O2 sensor output voltage.

The post-cat O2 sensors output voltage ranges between 0 and 1 Volt, with the level inversely-related to the oxygen in the exhaust stream when compared to the oxygen in the outside air. Consequently, when the oxygen level in the exhaust stream is relatively low, the sensor voltage is high (e.g., >0.6 V), and when the oxygen level is relatively high, the output is low (e.g., <0.4 V).

Ideally, an engine would burn all the fuel and oxygen that enters the cylinders, but this, of course, doesn't happen. There's usually some oxygen left along with other harmful by-products of the combustion process. Catalytic converters are used to reduce the remaining harmful emissions.

Catalytic converters have gone through a number of improvements over time, and one function of the later 3-way cats used in our Subarus is to store/consume any oxygen that's left after combustion and use it to "catalyze" certain harmful emissions. As a result of storing (or using the stored) oxygen, there shouldn't be much oxygen left in the exhaust after the cat(s).

If the voltage from an O2 sensor at the downstream end of a properly-operating cat system is high it suggests that the oxygen is either being stored or consumed, as it should be. However, if the O2 sensor output voltage is consistently low, it's indicating there's a relative excess of oxygen in the exhaust, which isn't as it should be. Similarly, if the rear O2 sensor voltage is fluctuating widely, while the pre-cat sensor is stable, it could mean the oxygen content in the post cat exhaust is changing, perhaps because the cat isn't lighting off steadily so for some of the time it's using the oxygen, and at other times it's not.

Just some ideas that I use when looking at logs . . .
 
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