Thread: Engine Harness Question

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  1. #1 Engine Harness Question 
    GT Level Member Hurricane87's Avatar
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    I found out recently that even though the GXP has the same powertrain all four years, it has a different wiring harness for each of the four years.

    Does anyone know why?
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  2. #2 Re: Engine Harness Question 
    Turbo is the way to go. Fivefingerdeathpunch's Avatar
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    I'm not aware that they changed year to year but they are surely different from 2005-2006 and 2007-2008.

    The 2005-2006's use a E40 computer with a different cam/crank trigger than the 2007-2008's that run a E67 computer with the newer 58/4x trigger pattern. The engine and transmission harnesses are different because of that.

    SMGPFC Member #1
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  3. #3 Re: Engine Harness Question 
    GT Level Member Hurricane87's Avatar
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    The GM parts guys say the 2006 is unique to its year, which means the 2005 would have to be, as well. Looking up the part number for the 2008 harness (which I had to do because the one I bought came with a superseded part number) says 2008 only, which means the 2007 is unique, as well. Pontiac Grand Prix Harness. Engine wiring. Harness, eng wrg - 25838081 | Wholesale GM Parts Online, Louisville KY

    I also think it's interesting that this part is good for the Super, but not the Impala SS of the same year.
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  4. #4 Re: Engine Harness Question 
    GT Level Member Hurricane87's Avatar
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    Related question, or maybe not. I have a crapload of codes. Most of them are O2 sensors, but some I've never seen before--C3064, C2174, C342D. I look these up and I get all kinds of different answers as to what they are. Is it possible these are related to the wiring harness being bad, or do I just have sensors committing hara kiri all at the same time throughout the engine bay?
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  5. #5 Re: Engine Harness Question 
    GXP Level Member Turbocharged400sbc's Avatar
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    C codes are usually the chassis/BCM/coms
    P codes are powertrain

    most will probably be involving the serial/CAN bus com/handshake issues.

    be aware that ground loop issues play havok with CAN bus data
    ~James~ Psychotic Gearhead
    projects: 84 Cressida waGN~ 90 LN3 3800, equal length headers, T70, 89 700r4, misc parts,
    1994 Oldsmobile 442 (462ci-4wd-2 engines) L67/4t80e^2,
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  6. #6 Re: Engine Harness Question 
    GXP Level Member Turbocharged400sbc's Avatar
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    as for the years, being short/special production there were likely lots of running changes to the harness' 05 didnt get the charging current sensor, 06+ did, harness now has new part number, 3 wires, 1 sensor, new part number.

    when GM figured out that they could use much thinner/cheaper 22 gauge wire for their engine bays (without impacting the 60k warranty with corrosion issues/etc....who cares about what it'll do when at 150k and 15 salty winters later....) they changed the harness part numbers, even though the wire routing/etc was the exact same. it was just cheaper to make.

    cars that experience harness chaffing issues will sometimes be wrapped differently/longer wires/additional mounting clips. new part number.

    only way yer gonna know for sure is to look at the diagrams
    ~James~ Psychotic Gearhead
    projects: 84 Cressida waGN~ 90 LN3 3800, equal length headers, T70, 89 700r4, misc parts,
    1994 Oldsmobile 442 (462ci-4wd-2 engines) L67/4t80e^2,
    00 Turbo Regal 608 fwhp 575ftlbs at 5500rpm, 98 WhippledRiv, 97 GTP
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  7. #7 Re: Engine Harness Question 
    GT Level Member Hurricane87's Avatar
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    So is there an actual part called a CAN bus, or is that just the name for the effect of all the computers tied together? And how do I diagnose and narrow it down? I don't want to just throw parts at it.
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  8. #8 Re: Engine Harness Question 
    GT Level Member Hurricane87's Avatar
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    And yeah, harness chaffing should be my car's middle name.
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