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  1. #1
    Junior Member
    Join Date
    Jan 2008

    Diagnostic Engine Codes Related to O2 sensor?

    I'm a proud owner of an '03 HCH but i've recently been having problems with poor gas mileage. I was getting 40-50 mpg it has recently dropped to 30-35 mpg. I've ran diagnostic test various times and after I read the codes I erase them. When I start my car the service engine light comes back on and I get the same codes I did prior to clearing them. I found some info on the web in() regarding the codes but i'm not sure how accurate it is. They are as follows:

    P0134 Mod$11
    O2 Sensor
    CKT No Activity
    Band 1 Sensor 1

    P1166 Mod$11 (Primary O2 Sensor Heater Malf.)
    Manufact. Control
    Fuel Air Metering

    P1420 Mod$11 (Nox Absorptive Catalyst System Efficiency Below Threshold)
    Manufact. Control
    Aux. Emission Controls

    P1491 Mod$11 (Exhaust Gas Recirc.(EGR) Valve Insuff. Lift)
    Manufact. Control
    Aux. Emission Controls

    So I figure I would start with the O2 sensor which would probably be the easiest/cheapiest way to start. I called my local Honda dealership and they want around $400 for the O2 Sensor Kit!

    I would greatly appreciate any help with this, I know there must be another solution besides a $400 one. Thanks in advance. - bb (earth80)

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  3. #2
    Junior Member
    Join Date
    Oct 2006

    earth80: Before sinking any


    Before sinking any money on any of the potential culprits I would invest in a Service Manual for your car. You can find these online at a variety of places including eBay or you can get them at your dealer for an added $ premium. If you have trouble locating one please PM me and I will provide you with a reference source.

    The main reason I mention this is that the procedural checklists in each section walk you through the process of identifying the faults methodically instead of depending on strictly guesswork.
    When it comes to the fuel and the emission system, it pays to know for sure where the problem really is. These parts are typically VERY expensive, so you really only want to replace the one that is at fault.

    The other thing that is VERY important is that you get the latest software updates for your ECU, PCM, and IPU. There's no point taking care of the "mechanical" problem with a new part if the software that governs it is outdated and accelerating the failure to begin with. Correct?
    To get the updates you HAVE to go to a dealer. So, you may have to ponder your strategies a little more carefully and I suggest you always factor in the necessary work that most shade-tree mechanics either omit or just can't do. That is why you should have a Service Manual since it may help you assess what things you can do, and what things you must leave for the Pros.

    By the way, the O2 sensor is NOT the most expensive item that owners of Gen 1 Civic Hybrids have to deal with when those codes appear. The Catalytic converter is perhaps the most feared and should not be ignored.



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