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Thread: No Spark # 7

  1. #11

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    I have a scan tool that turns off the CEL, but as soon as the truck runs with the dead miss on #7 for a few seconds, it sets the p0300 code.

  2. #12
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    Quote Originally Posted by Rukee View Post
    I have a scan tool that turns off the CEL, but as soon as the truck runs with the dead miss on #7 for a few seconds, it sets the p0300 code.
    the p0300 is random miss fires. with this code most times it is a fuel delivery problem low fuel pressures.

    could also be restricted exhaust .

    I missed the random miss fire code mentioned by you . I just saw your #7 cylinder mentioned.

    P0307 is #7 cyl miss

  3. #13

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    Quote Originally Posted by j cat View Post
    the p0300 is random miss fires. with this code most times it is a fuel delivery problem low fuel pressures.

    could also be restricted exhaust .

    I missed the random miss fire code mentioned by you . I just saw your #7 cylinder mentioned.

    P0307 is #7 cyl miss
    okay, but fuel pressure is not going to kill the #7 coil ! Like I said the # 7 has no spark when checking with a timing light, all other cyl's do.

  4. #14
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    the PCM is not stupid . if you have a miss with the #7 cyl it will say so.

    so what is the fuel pressure ? any other DTC ..

  5. #15

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    It may very well have more then one cyl miss firing, but # 7 is all but totally dead. The timing light might flash once or twice a minute on # 7. Fuel pressure holds steady at 60psi. No other codes, but the service traction control is flashing in the MC.

    - - - Updated - - -

    I disconnected the coil harness and checked continuity between the harness plug and the coil plug, everything checks out. So now I need to check the engine harness. Does anyone has a wiring schematics for the ECM? There are three main plugs, it would be very helpful to know which plug and pins I should be looking at. Thanks in advance.

  6. #16

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    just for the heck of it I would switch the #7 coil with a known good coil. See if it is still doing the same thing or if you have a problem with the coil. Just because there is continuity does not mean that the coil is good.

    1995 Silverado 4x4
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    2005 Yukon XL Jet Power Programmer, Bilstein Shocks, Bilstein rear springs, Helwig Anti-sway bars, EGR Window Visors, EGR Hood Shield, Denali Headlights, Headlight harness upgrade, GE NightHawk Bulbs, White Night Rear lighting system, Russell Braided SS brake lines, PowerStop Brake pads, PowerStop cross drilled and Slotted Rotors, http://www.gmtruckclub.com/forum/sho...5-GMC-Yukon-XL
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  8. #17

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    Quote Originally Posted by Pikey View Post
    just for the heck of it I would switch the #7 coil with a known good coil. See if it is still doing the same thing or if you have a problem with the coil. Just because there is continuity does not mean that the coil is good.
    I bought a new coil for # 7. I wouldn't expect 2 coils in a row to be bad. But I can swap it easy enough with the one next to it.

    - - - Updated - - -

    Swapped with the # 5 coil and wire miss stayed at # 7. So I'm thinking engine harness. Like I said earlier, does anyone has a wiring schematics for the ECM (PCM)? There are three main plugs, it would be very helpful to know which plug and pins I should be looking at for that # 7 coil.

  9. #18
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    I have a diagram of the 2000 silverado 6 L engine wiring.

    this shows the black wire A as the ground of the coil. D is the 12 volts to the coil pink wire. B is called the reference low brown wire. and the C is the red wire this is the control .

    B and C go to the PCM ...if you have ground good and 12 volts then you will have to check at the PCM for wire/connector damage..

    B/C are specific to this cylinder. I guess that with a meter you could probe these PCM voltages to see how it is different than the working coils.

    using a O scope would be nice...

  10. #19

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    Quote Originally Posted by j cat View Post
    I have a diagram of the 2000 silverado 6 L engine wiring.

    this shows the black wire A as the ground of the coil. D is the 12 volts to the coil pink wire. B is called the reference low brown wire. and the C is the red wire this is the control .

    B and C go to the PCM ...if you have ground good and 12 volts then you will have to check at the PCM for wire/connector damage..

    B/C are specific to this cylinder. I guess that with a meter you could probe these PCM voltages to see how it is different than the working coils.

    using a O scope would be nice...
    Thank you for that. I do have a good ground on the black wire and battery voltage at the pink wire, so now it's down to either the B or C wire are broken, or the PCM is burnt out for the # 7 cyl. Anyone have a diagram for where the B and C wires for # 7 go into the PCM?

  11. #20
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    Quote Originally Posted by Rukee View Post
    Thank you for that. I do have a good ground on the black wire and battery voltage at the pink wire, so now it's down to either the B or C wire are broken, or the PCM is burnt out for the # 7 cyl. Anyone have a diagram for where the B and C wires for # 7 go into the PCM?
    so with that then remove get access to the PCM check all wires there and remove connectors to inspect for damage/corroded green wires/ rodent chewed etc..

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