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2001 Chevrolet Prizm Question: Just bought this car new. Check Engine Light came on OBDII PO420

 

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axe_ace, Bonham, TX, May 06, 2014, 14:26
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Just bought this car new. Check Engine Light came on OBDII PO420 (indicating inlet/outlet readings out of range.) So what's the most common cause of this particular failure? O2 sensor(s) bad? Catalytic converter bad? Ethanol fuel (need ECM 'flashed'?)
Don't want to just throw money at this problem - fixed my '94 Prizm with advice off of here (coil in distributor failing) so hoping somebody here had run into this enough to at least point me in the right direction - DIY (don't really trust too many shops, don't have the money, don't have the time...worked in them 35 years!)
Thank you so much for your time!

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  • Answer #1

    G. T. Service Center (4231 Answers) , Stephenville, TX - (254) 638-3236
    ProfessorG May 06, 2014, 16:55
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     Master

    Catalyst Efficiency Low: After 35 years I guess you wouldn't trust my shop either, Sorry just hate hearing that, that's how I make my living. Sorry

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    axe_ace, May 06, 2014, 20:36
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    *Chuckle* You're probably right! -I suppose I've gotten to old and grumpy too fast. I don't even have anything in by old toolbox (bag o' tricks...) that I'd need to come close to tracking down something like this - but just about any 'modern' facility it should be a piece of cake. I've known some really good techs in my time, and of course have seen -or heard of- too many that really don't give a shit, just want the gravy... maybe I need to be more trusting, but my estranged wife (it's her car she just bought)and our daughter have just gone through a bad luck streak with cars and shops that would make your head spin! (I'll admit that probably had more to do with their decisions about where to buy these cars from and where to take for service though. Too long a story to get into right here now anyway.) No, back in the day I had a good reputation and a good following- of course I took 'shortcuts' but I never ripped anyone off or left them with half assed repairs/service.
    Right now there is nothing I'd like better than a scanner that could get me into OBDII 'Global' and let me see the readings on the 2 O2 sensors- that would at least be a good start... What I'm worried about mostly is some fool getting in there and jumping to conclusions and throwing parts ("shotgun" method) at it- I really don't know anybody out this way and don't have the money to spend gambling that I'll find somebody competent the first time.
    I know that emissions repair is a huge part of the business, but when I got out of it we were just barely getting started in OBDI and a lot of that was proprietary (secret) anyway. My NIASE certs were: Heating and Air Conditioning, Manual Transmission and Transaxle,Automatic Transmission/Transaxle, Engine Electrical, Engine Performance, Brakes, Suspension and Steering,Engine Repair... (best I can remember anyway. Like I said, it's been a while.)Now it's just 'ASE' - has been a while, and going by that era in this technology- and the type of failure I'm dealing with- maybe you can see why I said what I did. I apologise that you took it as a personal affront to the whole industry... but, well, ...

    What I was hoping for was another 'magic cookie'- when I looked on here about a stumbling/hesitation on my little '94 Prizm enough people had encountered this problem to give me a really good (possible) cause for my problem. I'm terminally ill with kidney disease, on dialysis and all that crap, besides having had a stroke that's pretty well wiped out the right side of my body (well, hand and foot anyway.)Enough people had encountered the ignition coil causing the exact same symptoms as I was having, and even if it showed good-to-marginal when I ohm'ed it out... it did turn out to be the problem (would've started looking fuel most likely by the way it felt initially- but didn't add up...)Yanked the distributor one day, "ohm'ed" it out -showed within specs, but secondary borderline- put it back in, drove it until the new coil came, installed it- and voila! Good as new (or good as 135,000 should be at least- peppy little hamster wheel!)
    I know some good techs down in Dallas, but well, out here in Bonham...
    (I need to know why catalytic efficiency is low- not just somebody that can weld stainless...)
    Master meant a whole different set of certs back when I was one- no disrespect intended to your shop or your abilities. -Actually kinda nice that you stood up for yourselves.

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    May 06, 2014, 20:34
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     Master

    Sounds like a bad cat.

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    axe_ace, May 06, 2014, 20:43
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    Yeah I know it. I guess my plan of action is 1) check output on both O2 sensors ... depending what I find (no exhaust leaks, oil consumption, etc...) 2) Replace cat. and upstrem O2 sensor. 3) There has been a "flash" released for the ECM to address these with this problem -something to do with incompatibility with high levels of ethanol in the fuel- but that means a trip to the dealership. Thanks for the feedback (have you had one with this problem that that fixed?) Gen 8 'Rolla? Thanks.

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    csubak30, May 06, 2014, 21:09
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     Master

    Found this similiar issue on a 2002 Ford Escape and a Hyundai Sonata and 2003 Murano. Seems like a popular problem on ten plus year old cars. One was the downstream o2 the others were the cat. converter. :)

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    axe_ace, May 06, 2014, 21:46
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    Cool, thanks- I think perhaps after a visual inspection of ancillary stuff I'll get her (my wife) to pick up both O2's, clear and drive it and when/if it comes back on replace the cat with a Flowmaster or some mid-range unit. (I might still have a friend at Friendly Chevrolet- I hope- if they're still in business. Might try and look him up tomorrow.) If the stupid CEL will just stay off long enough to get the emissions test for MVI done that's all I'm going to worry about for right now. Yeah, thanks again- (or I'll put my insurance on it for a day and inspect it out here in Fannin County) BTW, what's the difference between emission and non-emission county stickers now a days? -A different color number or something?

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