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Car guys - Check Engine Light ???

Discussion in 'Off Topic [BG]' started by ::::BASSIST::::, Dec 28, 2011.


  1. Mike N

    Mike N Missing the old TB Staff Member Supporting Member

    Jan 28, 2001
    Spencerport, New York
    +1 to the posts from 68Goldfish.
     
  2. I'm a Honda mechanic, whenever the CEL comes on, it's a sensor issue. Nothing detrimental unless it's flashing while driving. I haven't skimmed the thread because I'm on my cell phone, but if it's an environmental thing, it's probably the cat. Many times things like tree limb, so, sticks or stuff like that can mess with the wiring to the O2 sensor. Could also be a gas cap. I'm not sure if that model has specific coded for O2 related issues or not.
     
  3. These are a given, when the CEL comes on, the ecu makes up for the fault by increasing fuel trim.
     
  4. Mike N

    Mike N Missing the old TB Staff Member Supporting Member

    Jan 28, 2001
    Spencerport, New York
    I don't think fuel trims would increase for an evap leak.
     
  5. Maybe, maybe not. I'm currently in school for Hondas, and that's just something we were told. Anytime the CEL comes on, fuel trim increases. Never told why, just said a "fail safe" type of thing.
     
  6. Mike N

    Mike N Missing the old TB Staff Member Supporting Member

    Jan 28, 2001
    Spencerport, New York
    There are so many things that can turn the SES light on other than a sensor itself..... like a vacuum leak, leaky injector, fuel pressure regulator etc....
     
  7. Mike N

    Mike N Missing the old TB Staff Member Supporting Member

    Jan 28, 2001
    Spencerport, New York
    So do I. Seems every thread like this winds up with a new 02 sensor being the cure. Nothing quite like loading up the diagnostic shotgun and firing parts at it..... which is what you'll get when you go to Vato Zone to have a car "diagnosed."
     
  8. 68Goldfish

    68Goldfish Supporting Member

    Nov 4, 2006
    Port Orchard WA
    OP, lol. Sorry bro. No yelling here.
     
  9. 68Goldfish

    68Goldfish Supporting Member

    Nov 4, 2006
    Port Orchard WA
    I just don't know what good buying a scanner is going to do. You'd be better off spending your money on a good mechanic. Supposing you buy the scanner and you read the code. Then what? What are you going to do with any kind of evap codes or cat efficiency codes. How about missfire codes or system rich/lean codes. Even codes that have to do with sensors are usually circuit high/low or performance codes. Here's a secret.....there's no tool that you can plug in that will tell you exactly what's wrong with the car. If somebody offers that advise you should probably stop listening.
     
  10. Pilgrim

    Pilgrim Supporting Member

    You're right, code readers won't tell you exactly what's wrong in all cases - but there are some problems that do have fairly specific codes. And IMO no one loses by having MORE info about what the problem is. Tools like code readers provide information - and often give you as much info as a diagnostic would, except you get to keep the tool.

    And BTW to Port Orchard - Go, COUGS!
     
  11. True, all triggered by a sensor though. Trust me. I'm not questioning your knowledge, but with Hondas, a sensor will be the only thing to cause the light to come on. Like a leaky injector, might cause another sensor to trigger an abnormality and the light will come on. From that, further diagnosis will occur. I dunno though, I'm a little rusty on trouble codes. So you may be right, but off the top of my head, only a sensor can trigger the light. Sorta like an open header will show an airflow/emissions code, but that's by a sensor even though the header itself is missing or lose. See what I mean?
     
  12. 68Goldfish

    68Goldfish Supporting Member

    Nov 4, 2006
    Port Orchard WA
    Actually, nowadays you can get "code readers" or small scanners that can also do some data graphing for three to four hundred bucks. With that kind of a tool and a good DVOM and some service information you could get something done......depending on the problem.
     
  13. Mike N

    Mike N Missing the old TB Staff Member Supporting Member

    Jan 28, 2001
    Spencerport, New York
    I see what your saying, my point is while a particular sensor may have tripped a code, it doesn't mean that sensor itself is bad. I can't tell you how many Ford Windstar vans I've seen with codes for running lean (P0171 & P0174) that were a result of a vacuum leak at the intake manifold. Ford has a TSB out on this, and you can buy the updated gasket kit with the new front valve cover right from Ford and fix the problem.

    But, if the customer went to Vato Zone first (which too many people do) the wizards behind the counter would have sold them two 02 sensors, which would not have fixed the problem.
     
  14. Mike N

    Mike N Missing the old TB Staff Member Supporting Member

    Jan 28, 2001
    Spencerport, New York
    None of those scanners have bi-directional capabilities, so if you want to cycle evap solenoids through the PCM you're out of luck.
     
  15. 68Goldfish

    68Goldfish Supporting Member

    Nov 4, 2006
    Port Orchard WA
    Very true. And I like your ford example. That's something we don't have to deal with in the CDJ world of MAP sensors. If I have a vacuum leak the engine just idles faster. The PCM doesn't know the differance between measured airflow and non measured airflow. It just sees the drop in MAP and assumes the engine's under a load. If I have a vacuum leak I'll get codes for higher than expected idle speed, which in the case of a lot of newer hemi's and other chrysler engines with ETC is usually a stuck PCV valve. Hmm, another code that you couldn't just thow a part at.
     
  16. +1 O2 SENSORS
     
  17. hbarcat

    hbarcat Supporting Member

    Aug 24, 2006
    Rochelle, Illinois


    In my experience, the code usually tells me what's wrong. This past summer, the CEL came on in my van and it started running rough, but only after warm up. The code checked as faulty coolant temperature sender. A trip down to the parts store and ten minutes to replace the sender fixed the problem. Last year I had a similar situation with a faulty MAP sensor.

    Sure, stuff like vaccuum leaks are difficult to pin down but the code reader is a big help in diagnosing even these, with some mechanic experience. However, if you're a total newb with cars, you probably should just take it to the shop and have them deal with it, as you said.
     
  18. hbarcat

    hbarcat Supporting Member

    Aug 24, 2006
    Rochelle, Illinois


    This happens a lot. And O2 sensors are usually upwards of $100 each, aren't they?
     
  19. Bob Lee (QSC)

    Bob Lee (QSC) In case you missed it, I work for QSC Audio! Commercial User

    Jul 3, 2001
    Costa Mesa, Calif.
    Technical Communications Developer, QSC Audio
    Bad engine grounding can cause fault codes even if the sensors aren't actually bad or the parameters they read aren't actually out of whack.

    You see this a lot in the VW realm, where a lot of guys add mods to their engines and then do a real half-ass job reconnecting the grounds on the engine, chassis, and battery. The engine block and chassis are a reference point for many of the sensors, so any poor connections will add extraneous I*R noise voltages to those sensors' signals. These false readings will cause poor performance, fault codes, etc.

    I've seen this myself at a number of VW get-togethers. Some guy will show up, his engine looks really cool with a CAI (on a K04 turbo, no less ;)), shiny silicone breather hoses, FMIC, etc., and he's complaining that it runs like crap, he's got half a dozen random fault codes, he's been swapping out MAFs and injectors and everything, and nothing helps after hundreds of bucks spent. I put a DC voltmeter between the - battery post and the alternator body and read maybe 0.7 V with the engine idling and lights and accessories on. It should be maybe 0.05V at most. Well, there's the problem--it usually ends up being the connection between the chassis and block (the bellhousing, actually).
     
  20. ::::BASSIST::::

    ::::BASSIST:::: Progress Not Perfection.

    Sep 2, 2004
    Vancouver, BC Canada
    I had a mobile mechanic come and fix my brakes. I also asked him about the CEL and luckily he was able to help me with that. The code is P0118, if I recall correctly. The book said something about low coolent level in the radiator. We checked it out and it was low. We put some water in, the light went out, but then went back on again. This was about 4 days ago and the light is still on.

    Bummer.
     

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