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2005 Forester XS
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Discussion Starter · #1 ·
I had a used motor put into a new to me 05 forester xs . After driving it for a few weeks this code popped up. I haven’t noticed any problems besides a drop in mpgs. The cel turned off after nearly flooring it for a little stretch to open it up. The cel popped back up a few days later. This is the data currently.. How can I fix this?
Communication Device Gadget Mobile device Telephony Portable communications device Communication Device Gadget Portable communications device Mobile device Telephony Mobile device Communication Device Telephony Portable communications device Gadget Mobile device Communication Device Portable communications device Gadget Telephony
 

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2010 X Limited, 2.5L NA, 4AT. Purchased as the second owner in 2020 with ~126K miles.
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As far as I can tell, there is no indication of where the problem is in this data. 84 mph with 33.7% calculated load throws a flag for me. STFT 0%. Please share the details of your automobile. Particularly any mods. Are you trying to squeeze more out of this thing?
 

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2012 Forester 4 speed auto
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The Long Term Fuel Trim is at 20% and throws the code. What are the O2 readings for the upstream O2 sensor? Does this engine use a MAP or MAF sensor, or both. Does it use an O2 upstream sensor or a air fuel sensor?
 

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2010 X Limited, 2.5L NA, 4AT. Purchased as the second owner in 2020 with ~126K miles.
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533 Posts
The criteria for detection of the conditions to throw a P0171 on my 2010 is the difference between calculated A/F ratio and actual.

Rectangle Font Screenshot Parallel Technology
 

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2005 Forester XS
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Discussion Starter · #5 · (Edited)
As far as I can tell, there is no indication of where the problem is in this data. 84 mph with 33.7% calculated load throws a flag for me. STFT 0%. Please share the details of your automobile. Particularly any mods. Are you trying to squeeze more out of this thing?
It’s a naturally aspirated 05 forester. All stock and I have no plans for any mods.
 

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2005 Forester XS
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Discussion Starter · #6 ·
The Long Term Fuel Trim is at 20% and throws the code. What are the O2 readings for the upstream O2 sensor? Does this engine use a MAP or MAF sensor, or both. Does it use an O2 upstream sensor or a air fuel sensor?
I’m not sure how to check any of that. But I’ll look into it
 

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2005 Forester XS
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Discussion Starter · #7 ·
The criteria for detection of the conditions to throw a P0171 on my 2010 is the difference between calculated A/F ratio and actual.

View attachment 558493
I’m having trouble translating the abbreviations on my scan tool. Do the pics I posted show that I’m getting 5% more fuel while at 3300 rpms than I should be?
 

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2010 X Limited, 2.5L NA, 4AT. Purchased as the second owner in 2020 with ~126K miles.
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I’m not sure how to check any of that. But I’ll look into it
You can probably read the O2 Sensor live data @ "O2S B1S1" on your scanner. The 05 Forester uses a MAF sensor. Where did you get the 5% number?

EDIT: I've made a mistake on reading STFT. It is 7.8%.
 

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2005 Forester XS
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Discussion Starter · #9 ·
You can probably read the O2 Sensor live data @ "O2S B1S1" on your scanner. The 05 Forester uses a MAF sensor. Where did you get the 5% number?

EDIT: I've made a mistake on reading STFT. It is 7.8%.
Sorry I meant 7.5
You can probably read the O2 Sensor live data @ "O2S B1S1" on your scanner. The 05 Forester uses a MAF sensor. Where did you get the 5% number?

EDIT: I've made a mistake on reading STFT. It is 7.8%.
sorry that 5% can be disregarded hahah. What is the “measured value (g(oz)/rev)”? On that chart?
 

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2010 X Limited, 2.5L NA, 4AT. Purchased as the second owner in 2020 with ~126K miles.
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Well, let's look at this, then. Your fuel trims are all indicating a rich condition is being commanded by the ECM. Anything above 0% is considered rich. The ECM is pumping fuel into the engine and it still can't tell if it is too much, apparently. You are saying mpg is not normal. The deduction would be that the O2 sensor is not reading correctly. At this point, the downstream O2 sensor is still running fine at around 7 volts. So the catalytic converters are scrubbing the excess fuel out of the exhaust (assuming an accurate reading from the O2S B1S2). So the question is, what readings are you getting from O2S B1S1 (the upstream O2 sensor).

As far as the attachment, I don't know what that number is about. "Engine load". The map is a prerequisite parameter for alarm to sound. It's like, the car has to be running for the alarm to trigger. Important part is that the alarm is triggered by an out of limit condition when the ECM commands for air/fuel mixture don't match the return signal from the O2 sensor.
 

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2005 Forester XS
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Discussion Starter · #11 ·
Well, let's look at this, then. Your fuel trims are all indicating a rich condition is being commanded by the ECM. Anything above 0% is considered rich. The ECM is pumping fuel into the engine and it still can't tell if it is too much, apparently. You are saying mpg is not normal. The deduction would be that the O2 sensor is not reading correctly. At this point, the downstream O2 sensor is still running fine at around 7 volts. So the catalytic converters are scrubbing the excess fuel out of the exhaust (assuming an accurate reading from the O2S B1S2). So the question is, what readings are you getting from O2S B1S1 (the upstream O2 sensor).

As far as the attachment, I don't know what that number is about. "Engine load". The map is a prerequisite parameter for alarm to sound. It's like, the car has to be running for the alarm to trigger. Important part is that the alarm is triggered by an out of limit condition when the ECM commands for air/fuel mixture don't match the return signal from the O2 sensor.
It has a fresh front o2 sensor. I replaced it a few weeks ago.
 

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2010 X Limited, 2.5L NA, 4AT. Purchased as the second owner in 2020 with ~126K miles.
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Can you get a live data reading from your scanner? This will allow you to see if a fault exists.
 

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2010 X Limited, 2.5L NA, 4AT. Purchased as the second owner in 2020 with ~126K miles.
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Numbers fluctuating around 1.0 is a normal condition. Greater than 1.0 is lean, less than 1.0 is rich.
 

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2005 Forester XS
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Discussion Starter · #15 ·
Numbers fluctuating around 1.0 is a normal condition. Greater than 1.0 is lean, less than 1.0 is rich.
With it in park idling. It’s about 91f out. Ac off.
Fuel Sys 1.. cl
Fuel Sys 1.. n/a
Calc load.. 3.1%
ECT.. 201— 203F
STFT B1.. -0.8— 0.0%
LTFT B1.. 5.5— 6.3%
MAP.. 9(inHg)
RPM.. 725
Speed.. 0
Spark Adv.. 15.0— 16.0
IAT.. 149— 151F
MAF.. 0.40— 0.42
TPS.. 12.9%
O2SLoc.. O2S11/O2S12
O2S B1 S2.. 0.155— 0.715V
STFT B1 S2.. 0.0%
OBDSup.. OBD2
LAMBDA B1 S1.. 0.986— 1.000
O2S B1 S1.. 2.720— 2.794V
LAMBDA B1 S1.. 0.986— 1.000
O2S B1 S1.. -128.00— 127.99mA
 

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2010 X Limited, 2.5L NA, 4AT. Purchased as the second owner in 2020 with ~126K miles.
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Okay, thanks. "LAMBDA B1S1 0.986-1.000" is the number I was looking for. Are you in an alarm condition, now?
 

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2010 X Limited, 2.5L NA, 4AT. Purchased as the second owner in 2020 with ~126K miles.
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I don't see anything wrong with those numbers. Maybe somebody else does.

My next step would be to take the car out on the highway and bring the engine up to 3350 rpm and see what happens. There's no need to go 84 mph, though. Just leave it in third or second gear. Mph is not a factor in the alarm condition. Keep your engine load steady though, like a minute. Save your readings, if you can. I am mostly interested in the same O2S B1S1 information.
 

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Discussion Starter · #18 ·
Okay, thanks. "LAMBDA B1S1 0.986-1.000" is the number I was looking for. Are you in an alarm condition, now?
I’m not sure what an alarm condition is. The cel is on with that code and no other symptoms or problems. And I’ll get back to you with that highway info!
 

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2010 X Limited, 2.5L NA, 4AT. Purchased as the second owner in 2020 with ~126K miles.
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Yeah, that is what I was asking. I would clear the CEL (officially DTC) before the next test run.
 
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