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2005 Outback Wagon with 2.5L NA Auto
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Discussion Starter #1 (Edited)
Replaced my front O2 sensor a year ago. Figured it might be the rear causing the issue (165K on the odometer). Replaced rear; cleared code. Wasn't long and the code threw again. Checked the voltage on the front O2 with an OBDII app and it reads between 0V and 0.95V and reacts quick, so no issue with the front. Fuel mileage has suffered only a little. Now I'm noticing that the temperature gauge is registering a little lower than what it used to register.

Is it likely that an open t-stat would throw the P2097 code? I think it could, but wanted to check with others to see if it's logical. Seems like the OBDII and O2 sensors would have to be pretty sensitive to adjust to the temperature that way, but I figure it's possible. Is the normal operating temp @ 270F for the Soobie?

Thanks for reading.

- TC

EDIT: Solution not found yet...... Thought it was a dirty MAF, but after cleaning it twice, still having issues. Will edit here once I find the issue. May have to break down and pay a garage to do the troubleshooting and find the cause..... $130!
 

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On the Super Mod Squad
2002 3.0 VDC Wag + 2018 2.5 Leg Ltd
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miles on this? what brand o2 sensors did you use?


last time in miles plugs / wires swapped?

something on the intake making it rich ? last time MAP/ MAF was inspected / cleaned?


@plain OM

@traildogck ?
 

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2005 Outback Wagon with 2.5L NA Auto
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Discussion Starter #3
Plugs and wires replace less than 10k miles ago. 164k miles on car. Head gaskets replaced 2 years ago. Maf last cleaned 15 k ago, but have new filter and maf cleaner at home ready to install. The voltages off the maf seem to be fine. No erratic readings. Could it be the tstat?
 

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On the Super Mod Squad
2002 3.0 VDC Wag + 2018 2.5 Leg Ltd
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26,305 Posts
Plugs and wires replace less than 10k miles ago. 164k miles on car. Head gaskets replaced 2 years ago. Maf last cleaned 15 k ago, but have new filter and maf cleaner at home ready to install. The voltages off the maf seem to be fine. No erratic readings. Could it be the tstat?
coolant getting overly hot on the dash gauge,...ever? (spikes and falls?) anything past 9 or 10 Oclock position?

plugs and wires are what brand? (subarus like NGK)

densos are OK for o2 sensors. (I am using them right now on my own 2002 H4).

______

this one has EGR,...I think. and maybe that is not clean/ a little clogged up.

is it a federal spec or a california/NY emissions state one? (do you know where it was originally sold?)
 

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2005 Outback Wagon with 2.5L NA Auto
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Discussion Starter #6
Lower 48 car. NGK platinum. No misfire codes. No egr Code. Top tier fuel always, so littl chance of egr blockage. 9 o’clock or lower, always. Usually just under 9; reaches it now, but seems a lot slower to warm up. Fuel still rich after cats light off, so now know it can’t be cats. Must be maf or another sensor that doesn’t get reported by OBDIi when it fails.
 

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. . . Is the normal operating temp @ 270F for the Soobie? . . .TC

270 F? No. The "normal" 9:00 o'clock position (or very slightly below) on the temperature gauge corresponds to an actual range of about 158 to 212 F.

Is your OBDII app indicating 270 F?
 

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2001 VDC Wagon - White pearl - 302,000 km
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Replaced my front O2 sensor a year ago. Figured it might be the rear causing the issue (165K on the odometer). Replaced rear; cleared code. Wasn't long and the code threw again. Checked the voltage on the front O2 with an OBDII app and it reads between 0V and 0.95V and reacts quick, so no issue with the front. Fuel mileage has suffered only a little. Now I'm noticing that the temperature gauge is registering a little lower than what it used to register.

Is it likely that an open t-stat would throw the P2097 code? I think it could, but wanted to check with others to see if it's logical. Seems like the OBDII and O2 sensors would have to be pretty sensitive to adjust to the temperature that way, but I figure it's possible. Is the normal operating temp @ 270F for the Soobie?

Thanks for reading.

- TC
The front O2 sensor will react much quicker than the rear (post cat) sensor. What were the crossover voltages on the rear sensor? Keep in mind that it won't display major changes until it goes into closed loop status. Even then, they will present in a much slower and less dramatic frequency.


270F is a super-overheated state. Most thermostats are rated to open ~ 190F give or take. You might occasionally see upwards of 215F, idling with the AC on in July, but not this time of year in the upper hemisphere.


I'm guessing 270F is a typo
 

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2005 Outback Wagon with 2.5L NA Auto
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Discussion Starter #10
Will have to log more information. Anybody know what voltage range the MAF should function within?
 

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2005 Outback Wagon with 2.5L NA Auto
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Discussion Starter #12
I will see if I can log airflows, but I’m looking for a faulty MAF and my thinking is the sensitivity, of impacted, would be reflected by the voltage range of operation. The g/s is calculated from the voltage? I’m guessing and have to play with my engine OBD app to see what’s possible.
 

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Yes, voltage is used to calculate air flow. If the sensor is not reading correctly, it would be reflected in both the indicated voltage and g/s.

There's a number of threads here that deal with the P2097 code. Have you done a search for the code and read through the related threads? There might be some clues.
 

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2005 Outback Wagon with 2.5L NA Auto
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Discussion Starter #14
There's a number of threads here that deal with the P2097 code. Have you done a search for the code and read through the related threads? There might be some clues.
Yes, I looked and looked across the web and got information overload and the information (confidently) and mostly pointed to the O2 sensor (both front and rear).

My Front O2 was reading 0.8V at idle and varied with load and RPM from there, thus the thrown code. High voltage means rich mixture (I think something like 0.99 would be the very maximum voltage, but don't quote me on that).

Removed the airbox cover from the car and used MAF cleaner on the MAF sensor (the match head in the airstream). Replaced the parts. Restarted car (took a little while since there must have been cleaner still on it) and my voltage in the front O2 sensor dropped to 0.03V at idle.

I had cleaned it 15-20k miles ago. Always did it as part of preventative maintenance. This code for this issue was a first for me. Had I found the OBD scanner beforehand, I may have not had to go through all this.

My suggestion for anybody facing the same issues, either get you an ELM compatible with your smart phone/tablet and get an app (mine was free on iPhone apps... not the greatest, but provided me what I needed - OBD Car Doctor with a WiFi ELM that I already had for use on my LR3).

Mystery solved: Dirty MAF sensor.
EDIT: NOT Solved!!!

Have cleaned the MAF twice; CEL triggered. So, figured I'd change the air filter just to see; CEL triggered.

How do I test the MAF to see if it's causing the issue? What else can I look for using the scan 'tool' to try to isolate the problem? Any ideas?
 

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Discussion Starter #15
For the record, the MAF has been replaced and the CEL is still coming on. I now have P0131 and P2097 popping up. I'm guessing that it's the heater on the front O2 sensor. Just have to figure out the easiest way to test it without throwing more money at it. Guess it's back to forum searches.
 

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. . .guessing that it's the heater on the front O2 sensor.
P0131 is related to a problem with the signal from the B1S1 A/f sensor element itself or the connections between the sensor element and the ECU.

My Front O2 was reading 0.8V at idle and varied with load and RPM from there, thus the thrown code. High voltage means rich mixture (I think something like 0.99 would be the very maximum voltage, but don't quote me on that).

Removed the airbox cover from the car and used MAF cleaner on the MAF sensor (the match head in the airstream). Replaced the parts. Restarted car (took a little while since there must have been cleaner still on it) and my voltage in the front O2 sensor dropped to 0.03V at idle.
When using the OBDII data stream from the ECU, the front A/F Sensor voltage signal should be around 2.7 V most of the time (warmed up idling, driving steadily). If you're measuring around 0.8 V then that's consistent with the P0131.

Is that the same sensor you replaced a year ago?

Is that a FED-spec or CA-spec emissions/exhaust system?
 

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Discussion Starter #17
P0131 is related to a problem with the signal from the B1S1 A/f sensor element itself or the connections between the sensor element and the ECU.

When using the OBDII data stream from the ECU, the front A/F Sensor voltage signal should be around 2.7 V most of the time (warmed up idling, driving steadily). If you're measuring around 0.8 V then that's consistent with the P0131.

Is that the same sensor you replaced a year ago?

Is that a FED-spec or CA-spec emissions/exhaust system?
Thanks for replying plain OM.

Yep. @ 0.8 V , on average, on the front O2 sensor.

Yep, that's the sensor I changed last year. I was convinced by other sources that there's very little chance it would fail in a year.

It's a FED-spec engine.

My next step is to check the connector, but I seriously doubt it's an issue since I make a habit of 'usually' putting electrical contact silicone in place to prevent corrosion in Mag Chloride country.

Do you think it's a bad front O2 sensor or likely something else?

- TC
 

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Fed-spec, so just two sensors; one (Front) A/F Sensor and one Rear O2 sensor.

I'm not sure how your scanner identifies the sensors; does it use B1S1 and B1S2? I want to be sure the descriptive terms we're using are understood. This is in relation to that 0.8 V, which for the Rear O2 Sensor, is in a normal range (0.6-0.9V) when the engine is warmed up and idling and when driving steadily/cruising. So there could be some confusion.

It's possible the sensor has indeed failed either from a defect or something external causing it to become faulty. What was the reason for replacing the previous one?

If the connectors are in good condition (e.g., plastic housings are intact), then it shouldn't be necessary to add anything to the contact area. (The Denso sensors I used have a rubber seal inside.)

What brand sensor did you install, and what electrical contact silicone did you use?

http://www.subaruoutback.org/forums/109-gen-3-2005-2009/463161-p2097-o2-sensor-going.html is also relevant.
 

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2005 18psi supercharged U5 Outback w/207k+ miles
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It would be interesting to see your long term fuel trims (A/F learning) if you are able to pull those .

That might help to determine if this problem is happening in the eyes of the pre cat O2 as well.
 

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Discussion Starter #20
Fed-spec, so just two sensors; one (Front) A/F Sensor and one Rear O2 sensor.

I'm not sure how your scanner identifies the sensors; does it use B1S1 and B1S2? I want to be sure the descriptive terms we're using are understood. This is in relation to that 0.8 V, which for the Rear O2 Sensor, is in a normal range (0.6-0.9V) when the engine is warmed up and idling and when driving steadily/cruising. So there could be some confusion.
Good catch. I was looking at the wrong screenshot. O2S1 and O2S2 are used in my scanner. O2S1 ranges from 0.73 to 1.45V with a response time at time of screenshot of 264.66 ms.

It's possible the sensor has indeed failed either from a defect or something external causing it to become faulty. What was the reason for replacing the previous one?
A P2097 code, as I recall, was the reason I replaced the pre-cat O2 sensor last year. Used a Denso sensor and Permatex Silicone for the electrical connector, IF it was used. I may have chosen to skip it if there was a rubber seal.

The P0131 is non-specific on the O2 sensor it's related to.
The P2097 is "Post Catalyst Fuel Trim System Too Rich."

Fuel mileage has changed on average from 28.7 to 27.8; almost 1 mpg, but that could be due to cold weather and warmups on 20°F mornings. Could it be dirty or faulty injectors? I've run BG33 through it pretty regular, but haven't cleaned the throttle body or done a professional injector cleaning, ever, and I've got nearly 168,000 miles on it.

I don't have the gauges to check fuel pressures and don't know how difficult it would be to check if I had the gauges.

I haven't back-probed the sensors to check for voltages because, based on the info the scanner is giving me, that doesn't appear to be a problem, EXCEPT for the P0131, which makes me think the front sensor may be at fault.

I've got a visit to a local garage for diagnostics on Monday. I will be taking it in with tail between my legs, but this one is just stumping me with the amount of time I have to invest into looking at things. Looks like I'll be paying $120 minimum to get it figured out......
 
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