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<ownershipDocument>

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    <periodOfReport>2016-01-08</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000932699</issuerCik>
        <issuerName>AMERICAN POWER GROUP Corp</issuerName>
        <issuerTradingSymbol>APGI</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001649633</rptOwnerCik>
            <rptOwnerName>Arrow, LLC</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>2747 PARADISE ROAD, SUITE 3604</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>LAS VEGAS</rptOwnerCity>
            <rptOwnerState>NV</rptOwnerState>
            <rptOwnerZipCode>89109</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

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            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>46047</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0.1108</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
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            <transactionDate>
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    <derivativeTable>
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                <value>2016-01-08</value>
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                <transactionPricePerShare>
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                <transactionPricePerShare>
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                </transactionPricePerShare>
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                <underlyingSecurityTitle>
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                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>5000000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
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                <directOrIndirectOwnership>
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        </derivativeTransaction>
        <derivativeTransaction>
            <securityTitle>
                <value>Series D-2 Convertible Preferred Stock</value>
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                <value>0.4</value>
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            <transactionDate>
                <value>2016-01-08</value>
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                <transactionFormType>4</transactionFormType>
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            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>220.4084</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>10000</value>
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                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
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            <exerciseDate>
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            <expirationDate>
                <footnoteId id="F6"/>
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            <underlyingSecurity>
                <underlyingSecurityTitle>
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                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>5510210</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>220.4084</value>
                </sharesOwnedFollowingTransaction>
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            <ownershipNature>
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                    <value>D</value>
                </directOrIndirectOwnership>
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        </derivativeTransaction>
        <derivativeTransaction>
            <securityTitle>
                <value>Series C Convertible Preferred Stock</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>0.2</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2016-01-08</value>
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                <transactionFormType>4</transactionFormType>
                <transactionCode>J</transactionCode>
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                <footnoteId id="F10"/>
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            <transactionTimeliness>
                <value></value>
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            <transactionAmounts>
                <transactionShares>
                    <value>155.795</value>
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                <transactionPricePerShare>
                    <value>10000</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
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            <exerciseDate>
                <footnoteId id="F7"/>
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            <expirationDate>
                <footnoteId id="F7"/>
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            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock, par value $.01 per share</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
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            <postTransactionAmounts>
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        </derivativeTransaction>
        <derivativeTransaction>
            <securityTitle>
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            <transactionDate>
                <value>2016-01-08</value>
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            <transactionTimeliness>
                <value></value>
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                <transactionShares>
                    <value>155.795</value>
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                <transactionPricePerShare>
                    <value>10000</value>
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                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
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            <exerciseDate>
                <footnoteId id="F8"/>
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            <expirationDate>
                <footnoteId id="F8"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
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                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>7789726</value>
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            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>155.795</value>
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            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
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        </derivativeTransaction>
        <derivativeTransaction>
            <securityTitle>
                <value>Series D Convertible Preferred Stock</value>
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            <conversionOrExercisePrice>
                <value>0.1</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2016-01-08</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>P</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
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            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>15</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>100000</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
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            <exerciseDate>
                <footnoteId id="F9"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F9"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock, par value $.01 per share</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>15000000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>15</value>
                </sharesOwnedFollowingTransaction>
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            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
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        </derivativeTransaction>
        <derivativeTransaction>
            <securityTitle>
                <value>Common Stock Warrants (Right to Buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>0.1</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2016-01-08</value>
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                <transactionFormType>4</transactionFormType>
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                <equitySwapInvolved>0</equitySwapInvolved>
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            <transactionTimeliness>
                <value></value>
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            <transactionAmounts>
                <transactionShares>
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                <transactionPricePerShare>
                    <value>0.1</value>
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                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
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            <exerciseDate>
                <value>2016-01-08</value>
            </exerciseDate>
            <expirationDate>
                <value>2021-01-08</value>
                <footnoteId id="F11"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock, par value $.01 per share</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>15000000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
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                <sharesOwnedFollowingTransaction>
                    <value>15000000</value>
                </sharesOwnedFollowingTransaction>
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                    <value>D</value>
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        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Arrow, LLC received 451,264 shares of Common Stock as a payment-in-kind dividend on 200 shares of the Series B 10% Convertible Preferred Stock owned at the time of the dividend payment date.</footnote>
        <footnote id="F2">Arrow, LLC received 46,047 shares of Common Stock as a payment-in-kind dividend on 20.4084 shares of the Series A Preferred Stock owned at the time of the dividend payment date.</footnote>
        <footnote id="F3">Pursuant to the terms of the Securities Purchase Agreement, dated as of January 8, 2016, among American Power Group Corporation, Arrow, Associated Private Equity, and a third accredited investor identified on the signature pages thereto, Arrow exchanged all of the shares of Series A 10% Convertible Preferred Stock and Series B 10% Convertible Preferred Stock of American Power Group Corporation owned by Arrow for an equal number of shares of a new Series D 2 Convertible Preferred Stock.</footnote>
        <footnote id="F4">Shares of Series A 10% Convertible Preferred Stock have no expiration date and are convertible at the respective holders' election.</footnote>
        <footnote id="F5">Shares of Series B 10% Convertible Preferred Stock have no expiration date and are convertible at the respective holders' election.</footnote>
        <footnote id="F6">Shares of Series D-2 Convertible Preferred Stock have no expiration date and are convertible at the respective holders' election.</footnote>
        <footnote id="F7">Shares of Series C Convertible Preferred Stock have no expiration date and are convertible at the respective holders' election.</footnote>
        <footnote id="F8">Shares of Series D-3 Convertible Preferred Stock have no expiration date and are convertible at the respective holders' election.</footnote>
        <footnote id="F9">Shares of Series D Convertible Preferred Stock have no expiration date and are convertible at the respective holders' election.</footnote>
        <footnote id="F10">Pursuant to the terms of the Securities Purchase Agreement, dated as of January 8, 2016, among American Power Group Corporation, Arrow, Associated Private Equity, and a third accredited investor identified on the signature pages thereto, Arrow exchanged all of the shares of Series C Convertible Preferred Stock of American Power Group Corporation owned by Arrow for an equal number of shares of a new Series D-3 Convertible Preferred Stock.</footnote>
        <footnote id="F11">If American Power Group Corporation has not filed a certificate of amendment to its Restated Certificate of Incorporation with the Secretary of State of the State of Delaware increasing the number of authorized shares of Common Stock from 200,000,000 to 350,000,000 shares by January 8, 2018, then the Warrants will remain exercisable until January 8, 2026.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Matthew van Steenwyk, Director, on behalf of Arrow, LLC</signatureName>
        <signatureDate>2016-01-12</signatureDate>
    </ownerSignature>
</ownershipDocument>
