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Old 03-17-2018, 03:05 PM   #1
AndrewCSantiago
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Exclamation FB20 2.0 MPG needle malfunctioning on the cluster.

Has anyone experienced this? It's jumping since the check engine light came on due to a P015A Code.

Replaced the O2 bank 1 sensor 1 as that seemed to be the issue but the car is still idling a little rough and the MPG needle is jumping rather then gradually and smoothly increasing/decreasing like it used too prior to the check engine light.

Help, lol...
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Old 03-17-2018, 05:10 PM   #2
flyboy1100
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changed only 1 sensor? should change both.

what brand did you use? Denso was OEM and what I used
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Old 03-18-2018, 09:27 AM   #3
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Purchased from Subaru.

Replaced the one that was reading off a code - Bank 1 sensor 1. Something about Delayed response RICH TO LEAN. Code was P015A and P015B.

Don't think the sensors are the problem tho.

Check engine light back on after driving 45 miles. I think there is a bigger issue.

Car is very hesitant when trying to accelerate and the MPG needle still jumping rather then the gradual flow while driving.

Back story.

Car sat for about 2 and a half months with only being started once per week for a duration of about 10-15 minutes. The vehicle was outside during the cold months of January and February and a week or so in March. Car had ZERO issues prior to sitting for that long. All of a sudden now this crap. I think it may be a vacuum leak some where, or damaged wire due to rodents some how or may need new spark plugs because the hot cold weather affected them, IDK?
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Old 03-18-2018, 10:39 AM   #4
flyboy1100
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Default FB20 2.0 MPG needle malfunctioning on the cluster.

Did you check the plugs? Ever been changed? How many miles?

Probably would have been better off letting it sit with a battery tender on the battery or battery unhooked imho because 10-15min of idle is just going to fuel dilute your oil and build up more condensation because it will never really get to temp.

Have you changed the oil too? Not that it would create this situation....

P015A/B:

Potential causes for this code to set are:
Defective O2 sensor(s) Burnt, broken, or disconnected wiring and/or connectors Defective catalytic converter
Engine exhaust leaks


Could have a faulty new 02 sensor or bad wiring. This isnt going to just be a hook it up to a scanner and find your problem, your going to have to physically start checking wires, plugs, etc.

Do you have a service manual? Probably has troubleshooting for this....well it does, but not super helpful

Gonna just have to start inspecting or if the dealer wont replace it for free might have to have them dig into it if you aren't capable for whatever reason

Last edited by flyboy1100; 03-18-2018 at 11:21 AM.
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Old 03-18-2018, 11:18 AM   #5
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Old 03-18-2018, 02:41 PM   #6
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WOuldnt hurt to check for vacuum leaks.

Could be that the gauge is working fine. Is you mpg really crappy? Cause if that's the case it's probably not the gauge.

Something is making it dump more fuel/less. Defamation check the o2 sensors.
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Old 03-18-2018, 03:39 PM   #7
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Thanks.

I replaced 1 o2 sensor (1st one) as that is the only one that gave off the code Bank 1 sensor 1. I think it may be the Spark Plugs. Have not changed them and from sitting so long, like you said with the insufficient run time, they probably got caked up and are no good. Oil and oil filter changed. Gas was replaced with BG44K to clean out injectors and ran full tank down before refilling with 93 - nothing. Also checked air filter, I use a K&N - that was clean and airbox was clean. Also tried cleaning my MAF sensor - nothing has helped. So I think it is either plugs need to be changed or vacuum leak. From all the hoses I checked, they seemed fine but who knows. I checked every visible wire and plug and they seemed fine as well but again, who knows.

Mileage is about 130K - Plugs were done approximately 60K miles ago and haven't since. I'm hoping it's just the plugs and nothing else man...

As far as the MPG needle jumping like it does, idk - air/fuel mix is obviously distorted and most likely is causing this? IDK... Taking it to Subaru tomorrow morning. Other then change the spark plugs I've done everything I possibly could lol... I'm no technician or mechanic lol...
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Old 03-18-2018, 07:17 PM   #8
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If it is running poorly then it will most likely be jumping around with possibly giving too much fuel then not enough and that will make your mpg gauge fly around. And if it is getting Ralph bad gas mileage than it is even more likely to be true.

I bet the gauge is fine. I would think the plugs would be fine after sitting I would really look for a vacuum leak.
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Old 03-18-2018, 07:29 PM   #9
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the MPG gauge is just the computer calculation, there is nothing behind it mechanically. if it is running poorly that will indicate poorly.

this car uses BOTH 02 sensors to determine fueling. but i think your issue is more the sensors or the wiring.

vacuum leak wouldn't make it respond "slow" it would make it too lean all the time. there isn't much in terms of vacuum hoses on this car anyway. if you have a vacuum gauge pull the brake booster and check it at fully warmed idle, should be a minimum of -17.7", i tested mine about a month ago and pulled -19.5"....at about 150k on the odo.

exhaust leak is possible too, you could hear that tick though, but worth a quick check.

pulling the plugs is easy enough to see how they look, mine were all very carbon fouled which is why i changed my 02's out before i ever set a code. if they look normal, then....

i really think you got a faulty 02 or bad wiring, but if you figure it out post back for sure!!!
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Old 03-19-2018, 09:10 AM   #10
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Quote:
Originally Posted by flyboy1100 View Post
the MPG gauge is just the computer calculation, there is nothing behind it mechanically. if it is running poorly that will indicate poorly.

this car uses BOTH 02 sensors to determine fueling. but i think your issue is more the sensors or the wiring.

vacuum leak wouldn't make it respond "slow" it would make it too lean all the time. there isn't much in terms of vacuum hoses on this car anyway. if you have a vacuum gauge pull the brake booster and check it at fully warmed idle, should be a minimum of -17.7", i tested mine about a month ago and pulled -19.5"....at about 150k on the odo.

exhaust leak is possible too, you could hear that tick though, but worth a quick check.

pulling the plugs is easy enough to see how they look, mine were all very carbon fouled which is why i changed my 02's out before i ever set a code. if they look normal, then....

i really think you got a faulty 02 or bad wiring, but if you figure it out post back for sure!!!
Going to try and get the plugs done today.

I don't think the o2 sensor is the issue, like I said. Same code pulled up after new sensor installed. What are the odds of both being faulty? Just doesn't make sense to me. I could see if the other sensor pulled up a code after the 1st one was replaced but nope, same sensor pulled up the same code - and the car is riding rough. The car is definitely running rich and not lean as you can smell the gas when started, it's strong. All research has pointed towards Spark plugs or Vacuum leak after countless hours of researching and the symptoms I'm experiencing. So I'll get the spark plugs done most likely today and be able to gauge what is next in the process of getting this issue resolved.

Gas mileage is horrible, MPG needle jumping like crazy, when accelerating the car is hesitant and struggling when 3,000 RPM's are reached. It seems like it has no power and will not pull. and the idle is rough up and down, even wile cruising the RPM's are rough.
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Old 03-19-2018, 11:43 AM   #11
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my mpg was crap and plugs were carbon fouled due to poor 02's, also had nearly 150k on them. got about 1k on the new 02's and mpg is back to as good as it ever was on 87, might go back to my 91 tune and test....but that isn't your issue.

get a vacuum gauge, they are cheap. test your idle vacuum on the brake booster, you will know if you have a leak right away. if you want more info and don't have a service manual i can screenshot the page that says all possible problems based upon vacuum needle fluctuation. I don't think this is your issue though...

chance of a new 02 bad is slim. but you could have a bad connection or wire

post up pics of your plugs when you pull them, I am curious
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Old 03-21-2018, 09:54 AM   #12
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Update -

Getting work done to car on Saturday but along with the other symptoms - Hesitation while accelerating, rough idling, getting very poor MPG and the MPG needle on the cluster jumping.

It's also stalling out after driving. So I'll drive to the store, turn vehicle off - return to vehicle from store and start it - it immediately stalls out.

SMH... I think my CAT may also be clogged or shot along with Spark plugs needing replacement (Which will be done Saturday along with smoke tests to check for vacuum leakage). Or the MAF metering is off and needs to be replaced. Jesus help me...

This is frustrating.
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Old 03-21-2018, 11:46 AM   #13
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Ignore MPG needle, it has nothing to do with your problem. It is just useful information calculated by the computer....

Hesitation, rough idle, poor mpg, these are your real problems. These point to a problem with air flow through the engine or maybe a fueling problem.

Fuel filter ever been changed in your 130k? could be lack of fuel pressure.

Could be plugged cat as you stated. I seriously doubt a vacuum leak because one large enough for your issues would be so evident by just the noise it would be impossible to ignore it. Pull brake booster, put a vacuum gauge on it, and test your pressure. I bet its fine. Listen to how that sounds, and a vacuum leak that large will set a check engine light code.......

I made a oil collector bottle a few years ago and had a slight vacuum leak, i set a code....

Plugged cat, maybe fuel filter (less likely), or O2 issues.
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Old 03-21-2018, 11:53 AM   #14
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If it is stalling when warm then it is either not getting enough fuel into the cylinders or the plugs aren't sparking well enough most likely.
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Old 03-21-2018, 12:21 PM   #15
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On my old 2000 Impreza, I had a lot of issues with hesitation etc - turned out to be an issue with the spark plug coil pack. Could that be an option in this case?

The test for that was to spray water on the pack and you could see a spark if they were bad.
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Old 03-21-2018, 12:41 PM   #16
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I'll have too see.

I'm getting Spark Plugs done this weekend. I may also have the PCV changed as well, as a lot of research is indicating that may also cause a lot of the symptoms the car's experiencing.

As far as the fuel filter? No - never done. And neither has the PCV. Honestly, I don't think it's a vacuum leak either. After The Plugs and PCV are done, if the problem continues then I guess it's fuel or bad cat related and not air. What a pain in the ass.
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Old 03-22-2018, 12:10 PM   #17
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fuel is also easy enough to test with a pressure tester. bad pressure = bad filter, but if that is good too, and it isnt a plug or coil problem, then i say most likely CAT.

expensive for our cars too
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Old 03-22-2018, 06:42 PM   #18
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ItCars been stalling after being warm shutting off then when trying to start back up.

Think part of the problem is the plugs. Other issue may potentially be pvc or cat. I'll find out this weekend and update all.
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Old 03-22-2018, 08:31 PM   #19
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That sounds like plugs with 200k, not 50-60k
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Old 03-28-2018, 09:29 AM   #20
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Car is currently at Subaru.

Throttle Body was cleaned up - issue still remains. They stated they need an additional 2 hours to diagnose the issue, SMH.
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Old 03-28-2018, 01:12 PM   #21
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cat or 02s is still my guess
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Old 03-28-2018, 01:58 PM   #22
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feel your pain though, i am currently looking at dropping in an engine in mine for oil burning.....
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Old 03-28-2018, 04:48 PM   #23
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Well, they changed the A/F sensor - and that fixed the MPG needle jumping, hesitation while accelerating and rough idle - However - pulling out of their parking lot - the check engine came back on LOL. So I need to drop it off there again tomorrow for them to see what the issue is.

I'm thinking its the connection on that 02 sensor that was ORIGINALLY REPLACED. I asked them about the CAT, they said, no they checked the cat and it was "Good". Guess I'll find out tomorrow now. UGH!
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Old 03-28-2018, 06:53 PM   #24
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A/F sensor is the one you originally replaced? A/F also know as Bank1S1....
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Old 03-28-2018, 07:45 PM   #25
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Nope, bank 1 sensor 1 o2 was originally replaced.

However issue resolved lol.

Stopped at AutoZone to have them run code and Bank 1 lean code, I think a P0171 code or something like that.

So checked under the hood and the MAF wasn't plugged in all the way. Once I unplugged it, blew the inside of the connector out and plugged it back in - all is well. So the issue was the A/F sensor all along.
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