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Thread: PO170 code and check engine light

  1. #1
    Join Date
    May 2009
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    Napa Valley, CA
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    168

    PO170 code and check engine light

    So as I was out wheeling at Shaver Lake with the NCLR guys I got a check engine light. Nothing felt different, truck runs fine. I went to an Indy shop and got it scanned. Guy said it had a PO170 code. Tells me it's fuel trim related. His answer was that he needed to reflash my ECU to fix it. Wouldn't it be better to start eliminating causes like MAF sensor or O2 sensors before messing around with ECU? Any help?
    2005 LR3 V8 SE w/HD pkg, Sasquatch rods, 275/65/18 GoodYear Silent Armor, Hi-Country sliders & compressor mount, custom roof rack, custom skidplates, magnaflow exhaust, 6K HID upgrade, 4 x Hella 500FF

  2. #2
    Join Date
    Feb 2006
    Location
    Denver, Colorado
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    5,637
    I agree, fix the problem, be it a vacuum or exhaust leak, possibly 02 related, but don't waste your money trying to make it go away by flashing the ECU which is just doing it's job.
    Mike

    Retired service manager, member of Solihull Society, SCLR, past member of the NCLR and the Santa Barbara 4Wheelers clubs.
    99 D2, 3" lift, CDL with Detroit,T.T. lockers, 4:11's,H.D. axles, custom ft/rear bumpers with sliders, a 9500 HSI Warn winch and 5 HID's.

    To DOWNLOAD the RAVE Manual, follow this link http://www.landroverresource.com/

    Rover Radio issues or IPOD Adapters http://home.valornet.com/splacket/index.htm

  3. #3
    Join Date
    May 2009
    Location
    Napa Valley, CA
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    Thanks Mike! I tend to agree with that. I would much rather find the problem then mess with the ECU because it sounds like its just telling me something is wrong...ie. "just doing its job".

    I thought it could be a vacuum leak because from the engine bay when I give it gas I do hear a little whistle that seems to be a vacuum leak type sound. It sure sounds like a vacuum leak but I can't find it anywhere!!! The car idles and run just fine which is weird? I checked all the hoses (visually) and couldn't see any cracks or anything. Any suggestions to finding a leak easier? On my twin-turbo Audi the vacuum leaks are easy to find because it runs like crap and by pressurizing the system and spraying everything with soapy water you just need to look for bubbles and voila! Not sure if the same could be done for the LR3...there are a lot less hoses and not as much pressure as my Audi (25psi) so I don't want to go too crazy.

    I took off my MAF and it was caked with dirty soot. I cleaned that up but the CEL still remains. Would replacing it be worthwhile?

    How do I check for faulty 02 sensor?...simply by replacing it and seeing if that fixes the problem?

    Sorry if these are noobish questions...
    2005 LR3 V8 SE w/HD pkg, Sasquatch rods, 275/65/18 GoodYear Silent Armor, Hi-Country sliders & compressor mount, custom roof rack, custom skidplates, magnaflow exhaust, 6K HID upgrade, 4 x Hella 500FF

  4. #4
    Join Date
    Apr 2008
    Location
    Seattle
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    355
    Haven't I read that it's a bad practice to clean the MAF and that it should just be replaced? Or is that the throttle body I'm thinking of...?

  5. #5
    Join Date
    May 2009
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    Napa Valley, CA
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    Not sure Houm.WA about that. I have heard of people cleaning the throttle body, I've even had mine cleaned before. Not sure about MAF sensors...only thing I have heard about them is that they are sensitive and wires can be fragile. I have seen some MAF cleaners out on the shelves. I was going to try one of those and see if it helps...if not, then find my vacuum leak and/or replace the MAF sensor and hope for the best. I was going to try and run it without the MAF sensor in place and see if anything changes. I would assume that if it was my MAF sensor that was faulty then removing it wouldn't make any difference, but if it was running fine and then once removed started to idle all weird then I know the sensor is okay. Am I correct in my theory??

    I looked at my O2 sensors and they look very corroded and rusted over, didn't see any signs of exhaust leaks or loose wires but the O2's look like they will be a b!tch to replace if I need to go that route.
    2005 LR3 V8 SE w/HD pkg, Sasquatch rods, 275/65/18 GoodYear Silent Armor, Hi-Country sliders & compressor mount, custom roof rack, custom skidplates, magnaflow exhaust, 6K HID upgrade, 4 x Hella 500FF

  6. #6
    Join Date
    Feb 2006
    Location
    Denver, Colorado
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    5,637
    If you cleaned the MAF and you think it may have been the problem, you have to go have the codes cleared, they won't go away on their own.
    Let us know what you find.
    Mike

    Retired service manager, member of Solihull Society, SCLR, past member of the NCLR and the Santa Barbara 4Wheelers clubs.
    99 D2, 3" lift, CDL with Detroit,T.T. lockers, 4:11's,H.D. axles, custom ft/rear bumpers with sliders, a 9500 HSI Warn winch and 5 HID's.

    To DOWNLOAD the RAVE Manual, follow this link http://www.landroverresource.com/

    Rover Radio issues or IPOD Adapters http://home.valornet.com/splacket/index.htm

  7. #7
    Join Date
    Feb 2010
    Location
    Yucaipa, CA
    Posts
    141
    Take your truck in and have them look at long term fuel trims on both banks, record those numbers then reset adaptations. Then get it checked for vacuum leaks. Have them do a smoke test on the intake, crankcase and exhaust system. An intake leak downstream of the MAF will cause a lean mixture, a leak in the crankcase (loose oil filler cap, leaky valve cover) will cause a lean mixture and an exhaust leak upstream of an O2 sensor can cause a lean mixture also.
    Most likely you have some sort of vacuum leak and it was exaggerated by the higher elevation/thinner air at shaver lake.
    Once you determine where the vacuum leak is have it fixed then go drive for a tank or more. Look at the long term fuel trims again, they should be close to 0%. If they are still reading high (8-20% range) and you don't have any vacuum leaks then start investigating sensors. Look at what values the sensors are reading and go from there.

    Don't replace any sensors yet. Don't worry if you cleaned your MAF. Look for vacuum leaks first. They are the root of your problem.

  8. #8
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    May 2009
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    Napa Valley, CA
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    So I bought a code reader and picked up P0170, P0171 and P0174. I cleaned the MAF, checked all visible vacuum lines and tightened all hose clamps, then cleared the codes... but within minutes the CEL came back on. I don't notice anything different with performance. I tried the seafoam but didn't seem to do much.

    I think most of you guys are correct and it could be a vacuum leak. I swear I can hear one coming from the PCV valve area. I'll have to keep looking for it because I can't see where it could be coming from. Ther nearest dealer is 1.5 hours away from me and I really don't want to go to an independant anymore. I am still having a nasty knock with my front end after "fixing" my bushings by an Indy so I'm reluctant to go get this "fixed". I haven't had the best luck lately with my dear Rover...

    Also, when I was searching I came across this http://www.youtube.com/watch?v=UPFM3ZJXZag what is this regarding? Thanks again for all your advice guys!
    2005 LR3 V8 SE w/HD pkg, Sasquatch rods, 275/65/18 GoodYear Silent Armor, Hi-Country sliders & compressor mount, custom roof rack, custom skidplates, magnaflow exhaust, 6K HID upgrade, 4 x Hella 500FF

  9. #9
    Join Date
    Feb 2012
    Location
    France Savoie
    Posts
    6
    Hi...

    This means that the fuel mixture is out of range, that it cannot adjust
    the mixture properly. Your goal is first to figure out if it's gone too
    lean or too rich, and you can usually tell that from the smell of the
    exhaust... metallic and sharp tends to be lean, fuel-smelling tends to
    indicate too rich. The problem is that you have to catch it when it's
    actually acting up.
    Mixture problems can be caused by vacuum leaks, injector problems,
    bad fuel pressure regulators, bad air mass sensors, clogged air
    filters, etc. And some of those problems are intermittent.

    The thing is that if there is a problem even for a short amount of time
    (say a dead spot in the pot on the air mass sensor), it will register a
    code.... but you will never be able to catch it while the problem is actually
    happening since it only happens for a fraction of a second.

    The key for intermittent problems is to use a scanner that actually reads
    all the parameters in the ECU and to drive around and watch them. Seeing
    the actual values going in and out of the ECU is about the only way to tell
    what is really going on.
    Marc.


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  10. #10
    Join Date
    Aug 2008
    Location
    new jersey
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    136
    I actually had a codes 170 171 and 174 few years back. It turned out to be a bad throttle body sensor .No problems since then...

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