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  1. #1

    Default P0300 @ highway speeds

    2003 silverado 2500HD 6.0L 4x2 ext cab - throwing a P0300 when driving above 40mph. Power is there. No unusual noises & such. Changed plugs & wires. Performed injector test @ local high school trades shop. Fixin to change fuel filter next. What else would cause code @ highway speeds? Thx.

  2. #2
    Sr. Engineer
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    Dec 2011
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    Default

    The dreaded 300.. could be fuel or spark related. Check fuel pressure .. at least 58 psi and hold .
    What kind of injector test? Check ..clean maf sensor . Best to check pressure go from there.

    ---------- Post added at 08:55 PM ---------- Previous post was at 08:53 PM ----------

    Could be dist. gear .

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