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  <xs:element id="psix_LossContingencyDamagesSoughtValuePerNegligentViolation" abstract="false" name="LossContingencyDamagesSoughtValuePerNegligentViolation" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="psix_ProductWarrantyRecoveries" abstract="false" name="ProductWarrantyRecoveries" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="psix_EffectiveIncomeTaxRateReconciliationOtherPermanentDifferencesPercent" abstract="false" name="EffectiveIncomeTaxRateReconciliationOtherPermanentDifferencesPercent" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:percentItemType"/>
  <xs:element id="psix_PreferredStockSeriesAuthorized" abstract="false" name="PreferredStockSeriesAuthorized" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="psix_DeferredTaxLiabilitiesIntangibleAmortization" abstract="false" name="DeferredTaxLiabilitiesIntangibleAmortization" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="psix_ContractWithCustomerAssetLiability" abstract="false" name="ContractWithCustomerAssetLiability" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="psix_ShareBasedCompensationArrangementByShareBasedPaymentAwardLiabilityInstrumentsOtherThanOptionsAggregateIntrinsicValueOutstanding" abstract="false" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardLiabilityInstrumentsOtherThanOptionsAggregateIntrinsicValueOutstanding" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="psix_LossContingencyStayCaseTerm" abstract="false" name="LossContingencyStayCaseTerm" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:durationItemType"/>
  <xs:element id="psix_AssetsAndLiabilitiesLesseeTableTextBlock" abstract="false" name="AssetsAndLiabilitiesLesseeTableTextBlock" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:textBlockItemType"/>
  <xs:element id="psix_ThirdShareholdersLoanAgreementWeichaiMember" abstract="true" name="ThirdShareholdersLoanAgreementWeichaiMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="psix_ProductWarrantyReimbursements" abstract="false" name="ProductWarrantyReimbursements" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="psix_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsExercisableNumber" abstract="false" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsExercisableNumber" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="xbrli:sharesItemType"/>
  <xs:element id="psix_GaryWinemasterVersusTheCompanyMember" abstract="true" name="GaryWinemasterVersusTheCompanyMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="psix_EffectiveIncomeTaxRateReconciliationTaxCreditNetOfStatuteExpirationsAmount" abstract="false" name="EffectiveIncomeTaxRateReconciliationTaxCreditNetOfStatuteExpirationsAmount" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="psix_RickLulloffVersusTheCompanyMember" abstract="true" name="RickLulloffVersusTheCompanyMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="psix_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsExercisableAggregateIntrinsicValue" abstract="false" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsExercisableAggregateIntrinsicValue" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="psix_CollaborativeArrangementInventoryPurchasedGoods" abstract="false" name="CollaborativeArrangementInventoryPurchasedGoods" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="psix_InventoryValuationReservesChargedToExpense" abstract="false" name="InventoryValuationReservesChargedToExpense" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="psix_ShareBasedPaymentArrangementNumberOfSharesReceivedShareOfCommonStock" abstract="false" name="ShareBasedPaymentArrangementNumberOfSharesReceivedShareOfCommonStock" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="xbrli:sharesItemType"/>
  <xs:element id="psix_ScheduleOfLongTermDebtAndShortTermDebtInstrumentsTable" abstract="true" name="ScheduleOfLongTermDebtAndShortTermDebtInstrumentsTable" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrldt:hypercubeItem" type="xbrli:stringItemType"/>
  <xs:element id="psix_OperatingLeaseAssetsAndLiabilitiesLesseeAbstract" abstract="true" name="OperatingLeaseAssetsAndLiabilitiesLesseeAbstract" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="psix_NumberOfBoardMembers" abstract="false" name="NumberOfBoardMembers" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="psix_FinanceLeaseLiabilityAndOtherLongTermDebt" abstract="false" name="FinanceLeaseLiabilityAndOtherLongTermDebt" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="psix_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionLiabilityInstrumentsGranted" abstract="false" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionLiabilityInstrumentsGranted" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:sharesItemType"/>
  <xs:element id="psix_WarehouseEquipmentMember" abstract="true" name="WarehouseEquipmentMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="psix_EnergyEndMarketMember" abstract="true" name="EnergyEndMarketMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="psix_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsExercisableWeightedAverageRemainingContractualTerm" abstract="false" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsExercisableWeightedAverageRemainingContractualTerm" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:durationItemType"/>
  <xs:element id="psix_TransportationEndMarketMember" abstract="true" name="TransportationEndMarketMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="psix_CustomerBMember" abstract="true" name="CustomerBMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="psix_InventoryValuationReservesRollForward" abstract="true" name="InventoryValuationReservesRollForward" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="psix_VariousShortTermBorrowingsMember" abstract="true" name="VariousShortTermBorrowingsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="psix_ScheduleOfLongTermDebtAndShortTermDebtInstrumentsLineItems" abstract="true" name="ScheduleOfLongTermDebtAndShortTermDebtInstrumentsLineItems" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="psix_LossContingencyDamagesSoughtValuePerIntentionalViolation" abstract="false" name="LossContingencyDamagesSoughtValuePerIntentionalViolation" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
</xs:schema>
