NOTE GUARANTY INSURANCE POLICY

Exhibit 10.5

AMBAC ASSURANCE CORPORATION

NOTE GUARANTY INSURANCE POLICY

Policy No. AB1053BE

For consideration received, AMBAC ASSURANCE CORPORATION, a Wisconsin domiciled stock insurance corporation (“ Ambac ” or the “ Insurer ”), in consideration of the payment of the insurance premium payable with respect hereto, hereby unconditionally and irrevocably guarantees, subject only to (i) proper presentation of a Notice in accordance with the terms of this Note Guaranty Insurance Policy (together with each and every endorsement, if any, hereto, the “ Policy ”) and (ii) the terms of the

Policy, the payment to, or at the direction of, the Indenture Trustee, for the benefit of the Holders of the Insured Obligations, that portion of the Policy Claim Amounts which are Due for Payment but are unpaid by reason of Nonpayment.

1. Definitions .

Capitalized terms used herein and not otherwise defined shall have the meaning assigned to them in the Insurance Agreement or, if not defined therein, in the Sale and Servicing Agreement, or, if not defined therein, in the Indenture, without giving effect to any subsequent amendment or modification thereto unless such amendment or modification has been approved in writing by Ambac. For purposes of the Policy, the following terms shall have the following meanings:

“ Affiliate ” shall mean, with respect to any specified Person, any other Person controlling or controlled by or under common control with such specified Person. For the purposes of this definition, “control” when used with respect to any Person means the power to direct the management and policies of such Person, directly or indirectly, whether through the ownership of voting securities, by contract or otherwise; and the terms “controlling” and “controlled” have meanings correlative to the foregoing.

“ Bankruptcy Code ” shall mean Title 11 of the United States Code.

“ Basic Documents ” shall mean the Sale and Servicing Agreement, the Certificate of Trust, the Trust Agreement, the Sale Agreement, the Insurance Agreement, the Indenture, the Spread Account Agreement and all other documents and certificates delivered in connection therewith.

“ Business Day ” shall mean a day other than (a) a Saturday or a Sunday, (b) a day on which the Insurer is closed or (c) a day on which banking institutions in New York City, Newport Beach, California, Wilmington, Delaware or in the city in which the corporate trust office of the Indenture Trustee under the Indenture or the Owner Trustee under the Trust Agreement is located are authorized or obligated by law or executive order to be closed.

“ Class A Notes ” shall mean, collectively, the Class A-1 Notes, the Class A-2 Notes and the Class A-3 Notes.

“ Collection Account ” shall mean the account designated as such, established and maintained pursuant to Section 5.1 of the Sale and Servicing Agreement.

“ Distribution Date ” shall mean, with respect to each Collection Period, the 15th day of the following calendar month, or, if such day is not a Business Day, the immediately following Business Day, commencing January 16, 2007.

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“ Due for Payment ” shall mean, with respect to any Policy Claim Amounts, such amount as is due and payable pursuant to the terms of the Indenture.

“ Final Scheduled Distribution Date ” shall mean, with respect to (i) the Class A-1 Notes, the December 17, 2007 Distribution Date, (ii) the Class A-2 Notes, the December 15, 2009 Distribution Date and (iii) the Class A-3 Notes, the August 15, 2012 Distribution Date.

“ First Distribution Date ” shall mean January 16, 2007.

“ Holder ” shall mean any registered owner of a Class A Note (other than a United Party).

“ Indenture ” shall mean that certain Indenture, dated as of December 1, 2006, by and between the Issuing Entity and the Indenture Trustee.

“ Indenture Trustee ” shall mean Deutsche Bank Trust Company Americas, not in its individual capacity but as trustee under the Indenture, and its successors and assigns in such capacity.

“ Insurance Agreement ” shall mean that certain Insurance and Indemnity Agreement, dated as of December 14, 2006, among the Insurer, the Issuing Entity, UACC, the Seller and the Indenture Trustee, in regard to the Class A Notes, as such agreement may be amended, modified or supplemented from time to time.

“ Insured Payments ” shall mean, (i) with respect to any Distribution Date, the aggregate amount actually paid by the Insurer to, or at the direction of, the Indenture Trustee in respect of the amounts set forth in clause (i) of the definition of Policy Claim Amounts for such Distribution Date and (ii) the aggregate amount of any Preference Amounts paid by the Insurer on any given Business Day.

“ Insurer ” shall mean Ambac, or any successor thereto, as issuer of this Policy.

“ Interest Period ” means with respect to any Distribution Date (i) for the Class A-1 Notes, from and including the prior Distribution Date (or in the case of the first Distribution Date, from and including the Closing Date) to, but excluding, the current Distribution Date, and (ii) with respect to the Class A-2 Notes and the Class A-3 Notes, from and including the 15th day of the preceding calendar month (or, in the case of the first Distribution Date, from and including the Closing Date) to , but excluding, the 15th day of the month of the current Distribution Date.

“ Interest Rate ” shall mean, with respect to (i) the Class A-1 Notes, 5.34% per annum, (ii) the Class A-2 Notes, 5.15% per annum and (iii) the Class A-3 Notes, 5.01% per annum (in the case of the Class A-1 Notes, computed on the basis of a 360-day year and the actual number of days in the related Interest Period and, in the case of the Class A-2 Notes and the Class A-3 Notes, computed on the basis of a 360-day year consisting of twelve 30-day months).

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“ Issuing Entity ” shall mean UPFC Auto Receivables Trust 2006-B, a Delaware statutory trust.

“ Late Payment Rate ” shall mean the lesser of (a) the greater of (i) the per annum rate of interest publicly announced from time to time by Citibank, N.A. as its prime or base lending rate (any change in such rate of interest to be effective on the date such change is announced by Citibank, N.A.), plus 2% per annum and (ii) the then applicable highest rate of interest on the Class A Notes and (b) the maximum rate permissible under applicable usury or similar laws limiting interest rates. The Late Payment Rate shall be computed on the basis of the actual number of days elapsed over a year of 360 days.

“ Maximum Insured Amount ” shall mean $250,000,000 in respect of principal, plus interest thereon calculated at the applicable Interest Rate for the Class A Notes.

“ Nonpayment ” shall mean, with respect to any Distribution Date, Policy Claim Amounts which are Due for Payment but have not been paid pursuant to the Indenture.

“ Notice ” shall mean the telephonic or telegraphic notice, promptly confirmed in writing by telecopy substantially in the form of Exhibit A or Exhibit B , as applicable, to this Policy, the original of which is subsequently delivered by registered or certified mail, from the Indenture Trustee specifying the amount of any Policy Claim Amount which shall be due and owing.

“ Order ” shall have the meaning given such term in Section 8 hereto.

“ Person ” shall mean any individual, corporation, limited liability company, estate, partnership, joint venture, association, joint stock company, trust (including any beneficiary thereof), unincorporated organization or government or any agency or political subdivision thereof.

“ Preference Amount ” shall mean any interest on or principal of the Class A Notes which has become Due for Payment, the Nonpayment of which would have been covered by the Policy, and which was made to a Holder by or on behalf of the Issuing Entity which has been deemed a preferential transfer and recoverable, or theretofore recovered, from its Holder pursuant to the Bankruptcy Code in accordance with a final, nonappealable order of a court of competent jurisdiction; provided that any Preference Amount that constitutes interest shall be limited to the amount of interest on the outstanding principal amount of the Class A Notes (calculated at the Interest Rate for the relevant class of Class A Notes) accrued as of the last day of the applicable interest accrual period with respect to the Class A Notes and shall not, in any event, include any interest on the Class A Notes accrued after such date or any interest on such interest amount; provided , further , that in no event shall Ambac be obligated to make any payment in respect to any Preference Amount to the extent that such payment, when added to all prior payments of Policy Claim Amounts, would exceed the Maximum Insured Amount.

“ Preference Payment Date ” shall have the meaning given such term in Section 8 hereto.

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“ Reimbursement Amount ” shall mean, as of any Distribution Date, the sum of (x)(i) all Insured Payments paid by Ambac, but for which Ambac has not been reimbursed prior to such Distribution Date, plus (ii) interest accrued on such Insured Payments not previously repaid calculated at the Late Payment Rate from the date the Indenture Trustee, or any other Person at its direction, received the related Insured Payments or the date such Insured Payments were made, and (y) without duplication (i) any amounts then due and owing to Ambac under the Insurance Agreement, the Indenture and the Sale and Servicing Agreement, as certified to the Indenture Trustee by Ambac plus (ii) interest on such amounts at the Late Payment Rate.

“ Sale Agreement ” shall mean the Sale Agreement between UACC and the Seller, dated as of December 1, 2006, as such Sale Agreement may be amended from time to time.

“ Sale and Servicing Agreement ” shall mean that certain Sale and Servicing Agreement, dated as of December 1, 2006, by and among the Issuing Entity, the Seller, the Servicer, the Trust Collateral Agent, the Custodian, the Backup Servicer and the Designated Backup Subservicer, as the same may be amended or supplemented from time to time.

“ Scheduled Payments ” shall mean, with respect to any Distribution Date, an amount equal to the sum of the Noteholders’ Interest Distributable Amount (net of any interest shortfalls resulting from the application of Relief Act Shortfalls) and the Noteholders’ First Principal Distributable Amount (other than the amount specified in clause (2)(b) of the definition thereof) for the related Distribution Date; provided that Scheduled Payments shall not include (x) any portion of a Noteholders’ Interest Distributable Amount or of a Noteholders’ Interest Carryover Amount due to Holders because the Notice in proper form was not timely received by Ambac, or (y) any portion of a Noteholders’ Inter