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2003 Forester 2.5X 5MT & 2008 Impreza WRX 5MT & 2009 Impreza 2.5i 5MT
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77 Posts
Discussion Starter #1
I have a 2003 forester 2.5X 5 MT. I do not have the check engine light on, but today I connected my laptop to the car's ecu and fired up the FREEssm software. It returned a p0030 and said something about a temporary code. I do not have a check engine light on, but the car idles a little rough. I recently changed spark plugs, wires, etc. I mean the car runs good for it's age, but thought I try out this FREEssm with my laptop. I guess my question is since there is no check engine light on should I replace the front Oxygen Sensor/air fuel ratio sensor or why would I be getting this code without a CEL ??
 

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2007 Forester Sports XT 4EAT
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37,817 Posts

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Registered
2003 Forester 2.5X 5MT & 2008 Impreza WRX 5MT & 2009 Impreza 2.5i 5MT
Joined
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77 Posts
Discussion Starter #4
Yeah I did more googling and reading last night. I found on another Subaru forum where several people had a rough/low idle (i have the rough/low idle), but no CEL. Long story short they replaced the upstream air/fuel ratio sensor and the problem was solved.
 

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2007 Forester Sports XT 4EAT
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37,817 Posts
@greengoblin68 before you replace the front O2 sensor, try this. It only costs a bit of your time.

Bobby...

['07 FSXT Member Journal] ['03 X Member Journal]
 

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Registered
2003 Forester 2.5X 5MT & 2008 Impreza WRX 5MT & 2009 Impreza 2.5i 5MT
Joined
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77 Posts
Discussion Starter #6
Thanks for the tip. I did one better. Since I have owned this car the idle rpm has always been 650 that's a little low, so i broke out my android phone and the JDMscan apk. I went into ecu programming and set the engine rpm without a/c on to 750 I then restarted the car and verified the idle rpm is now at 750 I drove it around for 30 minutes to make sure it did not throw a CEL. It runs smother now, plus when the car is fully warmed up it has always stuttered a little from a dead stop. I think bumping the engine rpm up to 750 may have corrected that, because accelerating from a dead stop is alot smoother now. But thanks again to both of you for your suggestions
 

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Administrator
2007 Forester Sports XT 4EAT
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37,817 Posts

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Registered
2003 Forester 2.5X 5MT & 2008 Impreza WRX 5MT & 2009 Impreza 2.5i 5MT
Joined
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77 Posts
Discussion Starter #8
I'm not sure i understand your question Bobby. I wouldn't know how to program the ECU without the jdmscan. Is there another way to program it?

Also is that MT: 650 ± 100... 650 plus 100 ? Not sure what this means?
 

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Administrator
2007 Forester Sports XT 4EAT
Joined
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37,817 Posts
@greengoblin68 to clarify... the first USDM Forester ECM that could be programed by the user... that we could program, was on the '04 XT. That's why engine tuning prior to the '04 XT required a piggyback smart tuner. We had to install one on my son's '03 X when the AVO turbo kit was installed.

More here if you're interested in our '03 X Member Journal:
AVO Turbo Kit - Part 9b - Installation - the electrical

As to the idle speed...
MT - manual engine idle is 650 rpm, +or- 100 rpm. That means the idle can range from 550 rpm to 750 rpm.

Bobby...

['07 FSXT Member Journal] ['03 X Member Journal]
 
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