Subaru Legacy/Outback "Check Engine" Light Problems



  • xwesxxwesx Member Posts: 16,726
    I cannot offer feedback on most of your questions here, but as for "don't know what to do about any of it," I recommend that you simply write down the codes. You can read them without clearing them, which then leaves the codes in there. Or, you can read and then clear, which does turn off the CEL. Assuming no other problems, it should pass inspection.

    If you keep a log of the codes and dates/circumstances that may be involved with the code, you might be able to help a mechanic diagnose the problem. The codes themselves are symptoms and do not always point directly to the problem. If the light is on and you take it to a shop, they may very likely be unable to correctly diagnose and repair the problem They will, however, be far more likely to recommend work and throw parts at the problem.

    The code reader is not a replacement for repair and maintenance - it is a tool to assist those efforts.
    2018 Subaru Crosstrek, 2014 Audi Q7 TDI, 2013 Subaru Forester, 1969 Chevrolet C20, 1969 Ford Econoline 100, 1976 Ford F250
  • ateixeiraateixeira Member Posts: 72,587
    Indeed, get the code and Google them, or come here and ask if others have seen it.

    It helped me trouble-shoot a bad ignition coil once.
  • andydgandydg Member Posts: 2
    Followed the advice here and now own a memoscan U480, read the codes and erased them putting out the lights. VDC, CEL, flashing cruise light. Codes noted in case it repeats.

    Thanks guys some great advice here.

    Andy in the UK
  • gordon_junkiegordon_junkie Member Posts: 1
    i have a 1995 lagacy L station wagon, my check engine light stays on all the time. I had it scanned and was told it was the air flow senser which is connected to the air filter box. I replaced it and still have the same problem. Anyone got any suggestions??? I'm at a loss. Thanks.
  • 2009buyer2009buyer Member Posts: 15
    I got rid of my 1996 in January because of the same problem and the propensity of garages to charge for things cars don't need. The dealership looked at mine under warranty way back when and could never find anything wrong with it. Several people on this forum have advocated to buy a scanner and then just clear the codes and the light goes out. But mine went back on after about 100 miles. So unless you have to have it smogged and have the light out for that, just ignore it and go your merry way. I think it is a flaw in the car since mine had that problem from about 45, 000 miles to 188,000 miles. Great car anyway.
  • ateixeiraateixeira Member Posts: 72,587
    Do you recall the error code? P0400 something like that?

    These codes are merely reporting symptoms of a problem, not the actual problem itself.

    For instance, you may get a catalyst operating below an efficiency treshold error, but it could be a bad spark plug that doesn't burn all the fuel, so downstream the catalyst notes the presence of too much oxygen in the exhaust stream.

    The code does not mean the catalyst is bad, however.

    If we have a code it might help narrow it down at least.
  • gilson1gilson1 Member Posts: 4
    my 2002 Subaru Legacy Outback 149k has been giving me cel errors since 102k. Always passes emissions...have put in 3 cat converters...last one was "customized with a bigger biskit" Drove 149 miles turned it off for 5 days. started it up and light back on. car runs perfect and always passes emissions. Muffler shop is working with me but we can't tell what it is...last time it was suggested that it may be running rich causing the cat con to get too hot (some discoloration). this is a pain in the [non-permissible content removed] because I can't trade it in or sell it with that light on. looking for suggestions
  • ateixeiraateixeira Member Posts: 72,587
    First I'd try to reset just the light, see how long it stays off.

    If that fails I'd reset the ECU completely, see if that lasts longer.

    Then just trade it while the light is off. ;)
  • xwesxxwesx Member Posts: 16,726
    Have the oxygen sensors been replaced? If not, I suspect one or both may be giving a "false positive" on the catalytic converter. I assume you are getting the P0420 code, "cat below threshold." That code is generated when the oxygen differential between the fore and aft sensors is not great enough. As a result, the problem could be due to an inefficient cat, or it could be due to the sensors aging and lacking the sensitivity to provide accurate readings.

    I had that code for 50,000 miles on my Outback. Tailpipe emissions were within spec that whole time, so I fully suspect the sensors were the problem. I was going to replace them in the spring of 2007 but alas, fate had other plans. ;)
    2018 Subaru Crosstrek, 2014 Audi Q7 TDI, 2013 Subaru Forester, 1969 Chevrolet C20, 1969 Ford Econoline 100, 1976 Ford F250
  • dswissdswiss Member Posts: 11
    As you probably know, it could be a whole lot of things (last but not least one of the many oxygen sensors). Here is a little tip of what you can do to sell or trade it in: Reset the CEL by disconnecting the positive cable from the battery and shorting it for a few seconds to the chassis ground. Then reconnect it. That way the computer is reset and the CEL will be out and it will likely stay out for a few days.
  • gilson1gilson1 Member Posts: 4
    right on dswiss
  • xwesxxwesx Member Posts: 16,726
    Brilliant - dupe the next owner. We certainly need more folks with your mindset in our communities. :lemon:
    2018 Subaru Crosstrek, 2014 Audi Q7 TDI, 2013 Subaru Forester, 1969 Chevrolet C20, 1969 Ford Econoline 100, 1976 Ford F250
  • bobny57bobny57 Member Posts: 30
    After almost five years of trouble free driving I had the CEL flash.

    The dealer scanned it and reported Codes P2016-2021 Tumble Position Sensor 1&2 which would cost $611 plus tax to fix.

    My local mechanic is going to do the repair for $450 plus tax.

    Question: What is a tumble position sensor.

    Thanks for all the good advice you've given us over the years.
  • bobny57bobny57 Member Posts: 30
    An additional question regarding the tumble sensor: Is there anything I can do to insure that after I replace these sensors they won't be damaged again. For instance, should I replace my air filter, spark plugs etc.?

    Thanks again,
    Bob Woods
  • tommy69tommy69 Member Posts: 2
    i get a code saying misfire cylinder 3. any suggestions?
  • simonbonessimonbones Member Posts: 1
    I recently got the Check Engine light in my 2001 Subaru Outback. I read the code and got two of them:

    P0328 - Knock sensor circuit high input
    P0420 - Catalyst System Efficiency Below Threshold

    I'm not familiar with a Knock circuit but know it has something to do with ignition. I also know that the cat converter codes can go on an ignition problem. I'm weary to take this to a mechanic shop (since I haven't found a good one yet) and know they'll just try and get me to buy a whole new cat converter.

  • ragozcyragozcy Member Posts: 1
    Hey simonbones, a knock sensor is a piezioelectric sensor (when vibrated produces voltage). It's located directly on the engine block (usually right above cyl. 4) and senses misfires (engine knocking). It's odd you didn't get a misfire code, though, has it been running really rough in the past? Usually if it misfires badly enough, it'll knock out your knock sensor (P0328 almost always means the knock sensor is hooped, new one'll cost you anywhere from $180-$350) and consequently the extra fuel from cylinder that isn't firing will overheat and kill your cat (P0420). You could dish out the cash for the knock sensor, then ask around at exhaust shops for options on a new cat (or straight pipe with cheater chip)
  • golinegoline Member Posts: 9
    For almost 2 years my mechanic and I have been trying to fix this problem. We started with the gas cap. Then replaced the filler tube and valve and solenoid. The light stayed off for about 240 miles.

    After a smoke test (at another shop) we were told it was the fuel valve solenoid (again), that was replaced along with some canister that was attached to it and falling apart. The light stayed for a bit over 500 miles.

    After another smoke test last week (again, different mechanics shop...but same smoke test place), we're told it's the fuel filler tube and valve, again!

    I have started smelling gas over the past few months, did not smell it previously.

    As someone else mentioned, NYS has an annual safety/emissions test and my mechanic has had to work around my inspections to get the light off so I can drive a certain amount of miles and then hopefully pass the inspection before the light comes on again.

    I'd just keeping driving till next spring and inspection time, except for the gas odor which now has me scared.

    We also have a Forester and if and when I replace the OB, I will not buy another Subaru, even though we've love them up until this frustrating and expensive experience.

    BTW, my mechanic is well-known and respected in our area and I (kind of) have full confidence in him....I have another appt. with him on friday to bring the bugger in. ARGH!


  • golinegoline Member Posts: 9
    "it's what makes a Subaru, a Subaru." :cry:

    After my mechanics fourth attempt(in 2 years) to get the evap code off for good...after 82 miles it's back on again. I am not happy. :mad:
  • dswissdswiss Member Posts: 11
    here's a little tip:
    you can reset the check engine light by disconnecting the positive (red) wire from the battery and hold it to the ground for a second. Then reconnect. This will reset you computer. I did this just before inspection, and again before trade-in.
  • golinegoline Member Posts: 9
    Thanks for the tip....yes, it's been reset, but when it is ocurring during the inspection timeframe, you have to drive it some miles before the computer will accept the inspection. In NYS we have an annual inspection. What I'm really concerned about is the safety issue as there is a slight odor of fuel inside the car. We've had 2 smoke tests and using those results done those repairs to no avail. Everything's been tightened and closely inspected for cracks, leaking fuel, etc. It seems to come back on when I go on a longer trip than usual....over 50 miles or so. Just going back and forth to town (12 miles each way) doesn't seem to do it.
  • mikemasmikemas Member Posts: 6
    Please help on my 2002 Outback Sedan check engine does not turn on when i switch the ignetion on. It did not pass Smog yesterday because of CEL issue. Can somebody please advise.


  • ateixeiraateixeira Member Posts: 72,587
    Could be as simple as a bad bulb. Not easy to access, unfortunately.
  • mikemasmikemas Member Posts: 6
    Any other idea? the car run's great, i drove this car to LA last friday just got home early today. The car don't have any leakage at all, i did not feel anything about miss-firing.

    Thank you

  • mikemasmikemas Member Posts: 6
    Hello all,
    Again please help!!!!!!!! My 2002 Subaru outback sedan check engine light does not turn on when i turn the egnition on. The car run great, i did not feel anything about miss-firing no leakage for oil or any flued under the engine. the only problem that i have is it wont pass smog. Please advise.


  • ateixeiraateixeira Member Posts: 72,587
    Search on Scoobymods to see if anyone has instructions for taking the dash apart. Your problem is way too specific to find someone who can answer you.
  • dswissdswiss Member Posts: 11
    perhaps someone disabled it on purpose (like to sell the car to an unsuspecting buyer).
  • mikemasmikemas Member Posts: 6
    thank you.
  • mikemasmikemas Member Posts: 6
    thank you.
  • jemtecjemtec Member Posts: 40
    I know this thread is ancient, but I had to make a comment.
    The 1995 Subaru IS OBD-II compliant.
    Obviously the Person at Advance isnt aware that some cars made prior to 1996 (the official year ALL manufactures had to be OBD-II compliant) were OBD-II compliant before that mandatory year.
    Seeings how I myself own a 95 Subaru Legacy, and own a OBD-II reader, I can vouch that it indeed is OBD-II compliant.
    If you see the person again at Advance (provided this person is still working there) and tell them of this fact.
    Giving bad info to customers is a good way to make things way harder than they should be.
    Coming from an Autoparts store as a manager for 7 years, these kind of mistakes happen all the time with all the changes made.
    Small and large.
  • georgejunggeorgejung Member Posts: 8
    I've posted earlier on this thread.... then got side tracked. My 05 Legacy had a CEL several months ago - $300 later, had a new 'post convertor' sensor on, and all is well... for two weeks, when it happened again. After discussing it here, I took it to an Advance Auto Parts store, where they kindly did an OBDII scan - got the codes as follows.

    O2 sensor
    Circuit Low volts
    (Bank 1 Sensor 1)


    Post Catalyst
    'fuel Trim Bank 1
    System too Rich

    I read a manual - found the 'upstream' sensor and harness - difficult lil' bugger to reach. What I'm wondering now - is it the sensor ? Or is my cat convertor shot? It only has 21,000 miles on it. Any tips greatly appreciated!
  • fordwrenchfordwrench Member Posts: 70
    My '03 Legasy has set a P0507. I have already cleaned the throttle body and IAC. The CEL is on intermitantly now. I have never seen the idle speed hang too high. I priced an IAC at $300 ouch! Is there anything else that will set that code? I have checked for vacuum leaks, none, fuel trims are at 0 long and short, and I've checked for throttle cable misadjustment all ok. The car runs perfect and only has 63000 miles.It is a manual trans car by the way.
  • kks5kks5 Member Posts: 1
    I have gotten this code - well so many times that I cannot count - over the past 5 to 7 years on my 2001 Legacy wagon. I am not willing to spend the money to get a new Cat system, so I tried putting in a fuel line cleaner in. About a half a tank later it went off. I went to a different gas station and it was fine, but when I went back to the place that I filled up prior to the first time the light was back on after a quarter of a tank same code. So it seems to me, atleast with my car, it is quality of fuel.
  • alphabeta5alphabeta5 Member Posts: 1
    i had the same problem with my nissan xterra 2003. 2 codes P0328/P0420. already got knock sensor replaced. now the check engine light is back. really hate to pay 2k more to replace catalytic converter. i will check what's the current code.
  • mgc98legacymgc98legacy Member Posts: 2
    new to the forum, anyways i've got a 2.5 GT 1998 legacy that just recently began having the hazard lights, the dashboard, radio all start blinking when the car is off. I noticed that while this off the same clicking noise it makes off is also occuring while the car is running. the check engine light had been on, i had recently changed all the spark plugs, spark plug wire, and cooling system. The car runs fine with the check engine light on. I feel this is something to do with another aspect of the electronics system. any ideas??? i pulled the battery and put her to sleep for the night. thanks for any help!
  • mgc98legacymgc98legacy Member Posts: 2
    to clarify post #137 the check engine light is off now that everything is blinking. sorry, thanks
  • ateixeiraateixeira Member Posts: 72,587
    I wonder if it could be an alarm or remote keyless system malfunction? Change the battery on the key fob, perhaps?
  • cindy47cindy47 Member Posts: 2

    If you've still got te 2005 XT - you need to be very careful about the turbo. I have a 2005 Outback XT with 67K. I've been very good about changing oil and my turbo has now blown out. It's been in the shop for the last few days and I don't have a complete diagnosis yet, but I'm sure that it will be very expensive. Apparently there is a mesh screen in the banjo bolt that's in the turbo clogs and starves the engine of oil and bang - you've got a dead turbo on your hands. Looks like Subaru knows about the problem but hasn't been informing it's owners. Maybe this screen can be cleaned - if so it will save you much hassle. Just wanted you to be aware. I'll probably be posting more about my situation soon. :sick:
  • ateixeiraateixeira Member Posts: 72,587
    I think peaty has a mod for that on scoobymods, FWIW.
  • cansubcansub Member Posts: 1
    This car has about 50,000 miles and I have owned it since new and had it dealer maintained. The CEL came on recently, and apart from now running rough for a few minutes when starting from cold it runs reasonably well. I take it into the dealer on Nov. 6, and having read all the horror stories about trial and error part replacement in order to get the light turned off, does anyone have advice as to how I can avoid this happening to me.

    Any ideas as to what may be the problem.
  • gilson1gilson1 Member Posts: 4
    if it's cat/con before 100,000 Subaru should replace it. Mine blew at 102,000 and they wouldn't touch it. My closest Subaru dealer is a snake so that's the last place I'll ever take it or buy from.
  • chid_kidchid_kid Member Posts: 1
    My 2001 Outback had check engine light on for some time. It ended up being the O2 sensor. Much cheaper than a catalytic converter.
  • mburns01mburns01 Member Posts: 1
    I have a 2003 Outback with the 2.5L engine with 90k miles. At 75k the head gasket blew and based on other posts this issue is not uncommon. Now at 90k the engine keeps overheating when I go above 45 mph. I've had the radiator, water pump and thermostat changed based on my mechanics advice. Even after changing all these parts the engine is still overheating. The mechanic was stumped and called in Subaru and they said that they have seen some cases like this and that the engine is shot and needs to be replaced. I've never heard anything like this, the car idles and runs fine at slow speeds but once I start to cruise at speeds over 45 mph the engine will overheat. Has anyone else heard of a similar case?
  • ateixeiraateixeira Member Posts: 72,587
    If the engine overheated badly, it can happen. The heads can get warped.

    If it's not severe, they may be able to machine the heads so they're flat and true again.

    This would be the case for any alloy block (as opposed to heavy cast iron).
  • cindy47cindy47 Member Posts: 2
    Subaru did pay for the turbo. I had to pay for the labor. Since the turbo failed, I did have some metal shavings in the engine that left some scratches. But the dealer felt that I didn't have to do a major engine overhaul. The car is running great right now, but I fear that the catalytic converter will go next or something else. I've got 67K miles on this car...I was thinking I should probably replace the car in the spring -but I really don't want to. What are your thoughts?
  • ateixeiraateixeira Member Posts: 72,587
    It will probably be fine if the dealer thinks so, but if it makes you worry about it all the time, then go ahead and trade it in, because it's not worth the stress.
  • katielady22katielady22 Member Posts: 4
    Hi all,

    I posted this in another thread, but I've got an update and wondered what some of you thought.

    About 3 weeks ago, my "Check Engine" light came on in my 1997 Subaru Legacy. The day after the light came on, my temperature gauge in the car started slowly climbing, as if the car was overheating after 20 mins of driving. I turned on the heat and the temperature gauge went back to normal. I took it to have the code read, and it threw the P1502 code, which is for a radiator fan function problem. However, the temp. sensor and both the fans are functioning properly. I've checked the fluids, I don't seem to be having any leakage, and I just had the car tested for hydrocarbons in the cooling system and it came back clean.

    The car is fine on long drives and on the freeway but starts to overheat when I’m idling or in stop-and-go traffic. I was concerned that this might be a head gasket issue, but all the posts I've read about HGs have the car overheating at higher temps. Any thoughts? A friend suggested a flush, so I'm going to try that next. I'm loathe to take it in and rack up $$$ while someone digs around trying to figure out what the issue is.

  • doggrandmadoggrandma Member Posts: 144
    Do you live in an area where you have to buy fuel with ethanol? When I stopped using that and went back to "real" gas, our cars are performing much better and getting better gas mileage.

    Wonder when this ethanol boondoggle will end. Probably not until all our engines are destroyed. :(
  • xwesxxwesx Member Posts: 16,726
    It's a shame, really. What a waste of corn.
    2018 Subaru Crosstrek, 2014 Audi Q7 TDI, 2013 Subaru Forester, 1969 Chevrolet C20, 1969 Ford Econoline 100, 1976 Ford F250
  • bobny57bobny57 Member Posts: 30
    Thank you Cindy for the warning about the turbo. My experience after six years and 36,000 miles has been extremely positive and I'm going to hold my subie until it reaches at least 100,000 miles.
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