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Discussion Starter #1
Hi guys. Where is the relay between SBF5 and the upstream O2 sensor. Is it inside the ECU. I'm bout to pull my hair out diagnosing this p0030 code.
 

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Discussion Starter #5
Cool. Thanks. I'm sure it will.

Well all that did make me much more confident in my findings. But according to that chart my sensor is bad. It does however pass all checks to be good as far as I can tell if I test it by itself. This makes the second sensor I've purchased and its a denso. So I really don't think it is bad. Is there any sure fire way to make sure it is not the ecm that is acting screwy.
 

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I'm going to assume you installed a new Denso factory/OEM or Denso aftermarket OEM fit front O2 sensor.

Questions:

[1] Did you make the measurements, per the trouble shooting guide, to verify the wiring is good.
[2] Did you inspect the chassis wiring for damage. I recall one post where the cable was damaged... melted on the exhaust & shorting to ground.
[3] Have you had any issues with rodents chewing your engine wiring?

Bobby...

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

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Discussion Starter #7
So you guys can better help me I'll just start from the top. I'll try to keep it to the point. And just for your reference this makes my 5th Subaru having done cross year motorswaps to full deivetrain rebuilds, I love me some subies. Which is why when I came across a 03x manual tranny I couldn't pass it up. It was cheap because it had been wrecked on the front right side. Some minimal frame damage but nothing I'm worried about. And the car was kept pretty prestine prior to the wreck. Previous owner removed the catalytic converter, damaged in the wreck, and left the o2 sensor pigtails cut off and dangling in the engine bay. So the o2 sensor code did not surprise me. I got the car driveable, built an exhaust/W cat and ordered an upstream/downstream sensor set off eBay. Car ran great for about a day and then I noticed a vibration growing in the engine. That's about when my code came back. The upstream sensor failed the manufacturer's suggested test with the engine running using back probe method so I got a partial refund and kept the sensor. Then I ordered a denso OEM replacement/ universal splice in sensor. This sensor I spliced in to what I had of the original connector that had been left in the engine bay. Again ( i always clear codes after repairs) the car ran great, smooth as butter, but about the time the code came back it got ruff again and kept getting worse. To the point I fear I'll damage it if I don't fix it. And I've been trouble shooting ever since.

And sorry. To directly answer your question yes I followed the chart to a t, all my connections look good, and pretty sure no rodents.
 

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I posted this on your other your thread:
Disconnecting the battery or clearing a code with a scan tool resets the ECM. The ECM over time (run cycles) will relearn what was cleared & if the previous issues are redetected, from its attached sensors, you're back to where you started.
If this is what's happening, then the trouble has not been cleared.

It's possible the ECM is faulty, but the Subaru technical service manual doesn't provide any internal circuitry trouble shooting.
I have read where the ECM was at fault, but not specifically to this CEL trouble code.

The "red flag" for me is "wrecked" & "spliced in" O2 sensors. :icon_eek:

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

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Discussion Starter #9
Well thanks for the help man. Its good to bounce things off someone. The spliced in sensor concerns me slightly as well but it was a good price and I've used them before with good luck. My biggest concern is the progressive nature of the problem while at the same time being able to get it to go away entirely , or seemingly so, just by resetting the ecm. Its literally night and day driving it after a reset. And then how bad it runs seems to be directly proportional to the amount of time the car is driven. In my experience I've never had a Subaru act this way. If my sensor/s are bad I expect it to act that way no matter what. Clearing the code should have no effect if the sensor was truly bad. It'd just immediately kick the code again when the drive cycles were met. Right, someone please correct me if I'm wrong.
 

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Discussion Starter #10
Well guys... Hopefully if anyone has had as much trouble as me with the P0030 code they might find this thread normal. I plugged in my new to me ECM this past monday and so far it has transformed my subie. I now am getting 6 out of 7 monitors ready for duty when I only had 4 before. My cruise control finally works, now that I have no freeze or pending codes. Car is running smooth and doesn't show any signs of ruffness returning. I think its also important to note for some peoples benefit that I am getting these results running a nearly open custom, by me, exhaust and a universal Denso splice in O2 sensor that was purchased off ebay. So although a lot of people would point at those things they were ultimately irrelevant to my situation. Any way I hope this helps some future trouble shooters that who aren't getting anywhere solving the p0030.
 

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Well guys... Hopefully if anyone has had as much trouble as me with the P0030 code they might find this thread normal. I plugged in my new to me ECM this past monday and so far it has transformed my subie. I now am getting 6 out of 7 monitors ready for duty when I only had 4 before. My cruise control finally works, now that I have no freeze or pending codes. Car is running smooth and doesn't show any signs of ruffness returning. I think its also important to note for some peoples benefit that I am getting these results running a nearly open custom, by me, exhaust and a universal Denso splice in O2 sensor that was purchased off ebay. So although a lot of people would point at those things they were ultimately irrelevant to my situation. Any way I hope this helps some future trouble shooters that who aren't getting anywhere solving the p0030.
This thread does help a lot, having diagrams and such to reference to as someone is trying to diagnose that code. I recently started having cat and o2 sensor codes pop up. Started with a bad cat which I replaced. After that, both sensor started failing. I am currently on my 3rd upstream o2 sensor and have gone through p0031 and p0032 codes. Now I am stuck with p0030 code which, just like yours, I can clear and my car runs 10x better, but comes back on after about 30 miles or so. I will be looking into a new ECM, but first, a friend suggested I try using an o2 spacer to trick the system into thinking its running just fine. Any thoughts?
 

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@x9x3l1 where are you going to install that "O2 spacer"?

Also... take a look at this thread: P0030 Heater control circuit

Bobby...

['07 FSXT Member Journal] ['03 X Member Journal]
Thread it where the O2 goes in, in front of the cat and then thread the O2 in the spacer. I have never done this but I have read posts about this method and my coworker did this to his car and it worked.

I did read that thread you shared a couple days ago. Just after spending hundreds on a few sensor already, I guess I am a little bit discouraged to purchase yet another one for close to $200. But I will be placing an order on one of the Denso OEM this weekend.
 

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First, the P0030 CEL code is telling you there's an issue with the O2 sensor heater circuit. Take a look here: P0030 SUBARU - HO2S 11 Heater Control Circuit

Installing an O2 sensor spacer on the front, upstream Air/Fuel sensor won't correct a P0030 CEL code, it will cause other issues, as the sensor won't be correctly monitor the exhaust flow... your Air/Fuel mixture will be incorrect!

Normally the O2 sensor spacer is used on the rear O2 sensor as a "workaround". On the pre '05 that rear O2 sensor is only used to monitor the efficiency of the CATs... it monitors for excess 02 in the exhaust flow. Take a look at this thread: $5 fix (merged thread)

Also... if your head gaskets are starting to fail, any ingested... burned antifreeze will kill the O2 sensors & the CAT.

No need to buy a factory/OEM front O2 sensor. A Denso aftermarket OEM fit is the same sensor. These can be found on Amazon with free shipping. 😉

You can go here to find your Denso part number: densoautoparts.com Once you have the part number, you shop around for the best price.

Bobby...

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

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I have had bad luck with online purchases, being sent the wrong part or wrong connections rather than what I actually ordered. But I will do some shopping around. I hope that getting this Denso sensor will be the end of that. Thank you for your help and advice, much appreciated. :thumbsup:
 

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Update: Purchased and replaced the upstream O2 with a Denso OEM. Cleared CEL and the car ran really good for about 80 miles, until CEL came back on. Still getting the p0030 code. Should I be looking at the wiring leading to the ECM?
 

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Very strange that it works for 80 miles?

Questions:

[1] Is that P0030 the only CEL code you have?
[2] When you replaced the O2 sensor. Was the connector in good condition, as in, no corrosion & a solid tight fit?

If yes to the O2 connector question, then follow the testing on this post in this thread.

You might also start looking for a compatible replacement ECM. To be completely honest, I was never convinced the replacement ECM fixed the problem on this thread...

Bobby...

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