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Thread: Fuel tank 15-21 Colorado v6 (vacuum code?)

  1. #1
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    Fuel tank 15-21 Colorado v6 (vacuum code?)

    Is there a vacuum code associated with the current trucks gas tank?

    I want to add an auxiliary fuel tank and would plumb the pump to fill the oem tank through the gas filler.

    Since the trucks don?t have a gas cap, but a flapper, I?m hoping to not have any codes thrown.

    I have read that other current trucks with gas caps (Fords Tacoma?s Silverado?s etc) will through a code and I think it had to do with vacuum in the charcoal canister etc.

    If it does throw the code any ideas on how to fix things so there isn?t a problem. Not just turning the code off?

    Plumb the new fuel cell vent line to the oem vacuum side?

  2. #2
    Tuner TheMechanic's Avatar
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    You could do that but the total volume of the tank as it empties will be more than the programmed volume. There is a leakdown specification to give you a small or large leak.

    If the volume is increased without a change it will likely not throw the code for a small leak if you have one and or throw a small leak code if you have a larger one. It bases this on a predetermined leak down rate. Not sure if going into the "fuel" section and changing tank volume will automatically modify the EVAP system specifications/settings or not.

    In my Techline Connect I can go into GDS2 and force an EVAP test but not sure how many aftermarket scan tools can do this. I guess just playing around with it you will find out. As a rule you will need to plumb the second tank exactly like the first with a vent and purge line and sealed cap/new style capless filler.

    The new style filler really is just a different way to seal the filler neck when not refueling.

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    Thank you... (I really could bend your ear about if there is a way to reverse the pwm signal sent by the bcm from 0-90 to 90-0 like the holly can, and if there is a defroster part of the tune not in hptuner yet)..,


    I’m wondering if I have the second aftermarket tank... on its own pump etc, that when turned on, feeds into the fuel filler neck just below the flapper door (cap less system)... would it bypass this leak detection system?

    After all. How is that different than me pouring fuel in with a fuel can when the engine is still running?

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    Tuner TheMechanic's Avatar
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    Yes that would work as long as you had a vac/leak proof seal/solenoid/pump etc. that won't let the vacuum decay during it's test. You could of course just set all the evap codes to 3 no reporting though. I would personally just use your idea of the tank on a separate pump that refills. Only issue I could see is that the vehicle will see the tank refueling as it is being driven. Possibly causing an issue (IF) you were filling at the same time it was running the diagnostic monitor. Oh and of course if you overfilled you could get raw fuel in the vapor/charcoal canister causing its early demise.
    Not sure I am understanding your question about the BCM. Do you mean the ECM/PCM and purge or vent control?

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    So if I use a separate pump that dumps into the fuel filler neck, there will be no codes unless it is filling during a diagnostic moment?
    That would be awesome and ideal.

    When I mentioned the bcm I am actually referring to the pwm control of the radiator fans. Oem pwm signal is 0-90 (actually 4-90 I believe) but all aftermarket are inverse, 90-0...
    so in order to get a spal brushless to work, we have to inverse the fan part of the tune.

    But I don’t believe all of the tables are available via hptuner. So things like correct triggering of the fans during defrost isn’t perfect.
    I don’t know if there is something in the ecu or bcm that allows to change the signal it is sending from 0-90 to the spal signal or 90-0 (88-18 actually). That way all the sub functions will be working correctly and efficiently

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    Tuner TheMechanic's Avatar
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    Pump will work. As to the PWM I would imagine someone has a PWM signal conditioner or inverter that would modify/flip the signal to function before the current control device.

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    I wish. Ive been searching, but maybe my search terms were incorrect

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