<PAGE>
                                                                   EXHIBIT 4(g)6


                               FIRST AMENDMENT TO
                 SECOND AMENDED AND RESTATED SECURITY AGREEMENT

         This First Amendment dated as of September 7, 2001, by and between
Credit Acceptance Corporation, a Michigan corporation (the "Company"), the
Subsidiaries of the Company from time to time parties hereto (collectively, with
the Company, and either or any of them, the "Debtors" and individually, each a
"Debtor") and Comerica Bank, a Michigan banking corporation ("Comerica"), as
agent (in such capacity, the "Collateral Agent") for the benefit of the
"Lenders", the "Noteholders" and the "Future Debt Holders" (each as referred to
in the Security Agreement, defined below).

                                R E C I T A L S:

         A. Pursuant to the Credit Agreement and the Senior Debt Documents (each
as defined in the Security Agreement), Debtors executed and delivered to the
Collateral Agent that certain Second Amended and Restated Security Agreement
dated as of June 11, 2001 (the "Security Agreement").

         B. Debtors and the Collateral Agent desire to amend the Security
Agreement as set forth below.

         The parties agree as follows:

         1. Section 1.1 of the Security Agreement is amended, as follows:

         (a) The following new definitions are added to Section 1.1, and
inserted in appropriate alphabetical order:

         "CAC Canada" means CAC of Canada, Limited, a corporation organized
         under the laws of Canada.

         "Percentage Limitation" means the lesser of: (i) all of the shares of
         stock of CAC Canada owned or at any time and from time to time acquired
         by the Company or any other Debtor and (ii) sixty-five percent (65%) of
         the aggregate share capital of CAC Canada at any time or from time to
         time issued and outstanding determined in accordance with Section 956
         of the Internal Revenue Code of 1986, as amended from time to time, and
         the regulations promulgated thereunder.

         "Pledged Canadian Shares" means those shares of stock of CAC Canada
         from time to time subject to the security interest and lien established
         hereby, as set forth in Section 2.1(i) of this Agreement.

         "PPSA" means the Personal Property Security Act as in effect in the
         Province of Ontario; provided that if, by applicable law, the
         perfection or effect of perfection or non-perfection of the security
         interest created hereunder in the Pledged Canadian Shares is governed
         by personal property security legislation as in effect on or after the
         date hereof in any other jurisdiction, "PPSA" means the personal
         property security legislation as in effect in such other jurisdiction
         for purposes of the provisions hereof relating to such perfection or
         the effect of perfection or non-perfection.




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         (b) The definition of "Pledged Shares" is amended to add, in the third
line thereof (following the words "Non-Specified Interest"), the words "and the
Pledged Canadian Shares."

         2. Section 2.1 (i) of the Security Agreement is hereby amended and
restated in its entirety, as follows:

                  "(i)     (a) all shares of stock, and other equity,
                           partnership or membership interests constituting
                           ownership interests (or evidence thereof) or other
                           securities, of the Significant Domestic Subsidiaries
                           of Debtor from time to time owned or acquired by such
                           Debtor in any manner (including without limitation,
                           as applicable, the Pledged Shares), and any
                           certificates at any time evidencing the same, (b) and
                           65% of the issued and outstanding capital stock of
                           CAC Canada, as evidenced by the share certificate
                           described on Schedule D hereto and all additional
                           shares of stock or other equity interests in CAC
                           Canada issued after the date hereof to Company or any
                           other Debtor or otherwise from time to time owned or
                           acquired by Company or any Debtor in any manner,
                           subject, however, to the Percentage Limitation, and
                           (c) all dividends, cash, instruments, rights and
                           other property from time to time received, receivable
                           or otherwise distributed or distributable in respect
                           of or in exchange for any or all of such shares;"

         3. The last sentence of Section 3.4 of the Security Agreement is hereby
amended and restated in its entirety, as follows:

                  "All certificates or other instruments owned by such Debtor
                  representing shares of stock or other ownership interests of
                  any Significant Domestic Subsidiary (including, without
                  limitation, the Pledged Shares) or the Pledged Canadian Shares
                  or representing or evidencing the Non-Specified Interest will
                  be delivered to the Collateral Agent, accompanied by duly
                  executed stock powers or instruments of transfer or
                  assignments in blank with respect thereto."

         4. Section 3.7(c) of the Security Agreement is hereby amended and
restated in its entirety, as follows:

                  "(c) On the date hereof, the Pledged Shares constitute the
                  percentage of the issued and outstanding shares of stock,
                  partnership units or membership or other ownership interests
                  of the Issuers thereof indicated on Schedule D, if applicable,
                  and such schedule contains a description of all shares of
                  capital stock, partnership units, membership interests and
                  other ownership interests of or in CAC Canada, the Significant
                  Domestic Subsidiaries owned by the applicable Debtor and with
                  respect to the Non-Specified Interest in the Titling
                  Subsidiary (as such Schedule D may from time to time be
                  supplemented, amended or modified in accordance with the terms
                  of this Agreement)."

         5. Section 4.15(a) of the Security Agreement is hereby amended and
restated as follows [the changes are in bold]:






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                  "(a) except with the written consent of the Collateral Agent,
                  it will not permit CAC Canada or any Significant Domestic
                  Subsidiary to issue to it or any of its other Subsidiaries any
                  shares of stock, membership interests, partnership units,
                  notes or other securities or instruments (including without
                  limitation the Pledged Shares) in addition to or in
                  substitution for any of the Collateral, unless, concurrently
                  with each issuance thereof, but subject to the Percentage
                  Limitation in the case of the shares of CAC Canada, any and
                  all such shares of stock, membership interests, partnership
                  units, notes or instruments are encumbered in favor of the
                  Collateral Agent under this Agreement or otherwise (it being
                  understood and agreed that all such shares of stock,
                  membership interests, partnership units, notes or instruments
                  issued to such Debtor shall, without further action by such
                  Debtor or Collateral Agent, be automatically encumbered by
                  this Agreement as Pledged Shares) and"

         6. Section 6.1 of the Security Agreement is amended to add, after each
reference to the "UCC" in such section, the words "or the PPSA".

         7. Section 6.2(a) of the Security Agreement is amended to add, in the
seventh line thereof (after the definition of "Securities Act"), the words "or,
in the case of the Pledged Canadian Shares, the equivalent thereof, pursuant to
part XVII or Rule 45-501 of the Securities Act (Ontario), as amended from time
to time (the "Canadian Securities Act")," and to add, in the last line of such
section (following the words "applicable state securities laws"), the words "or,
in the case of the Pledged Canadian Shares, under the Canadian Securities Act,".

         8. Section 7.4 is amended to add in the second to last line thereof
(following the words "U.S. Mail,"), the words "or, in the case of the Pledged
Canadian Shares or CAC Canada, `Canada Post'".

         9. Replacement Schedule D (Pledged Shares) to the Security Agreement
set forth on Attachment 1 hereto shall replace, in its entirety, existing
Schedule D (Pledged Shares) to the Security Agreement.

         10. Except as expressly modified hereby, all the terms and conditions
of the Security Agreement shall remain in full force and effect. Except as
expressly set forth herein, nothing in this Amendment shall constitute a waiver
of any term or condition of the Security Agreement or any of the rights and
remedies provided to the secured party thereunder or as otherwise provided by
law.





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         IN WITNESS WHEREOF, the parties hereto have duly executed this
Amendment as of the day and year first written above.


                                    DEBTORS:

                                    CREDIT ACCEPTANCE CORPORATION


                                    By: /s/ Douglas W. Busk
                                    Name: Douglas W. Busk
                                    Title: Treasurer
                                    Address for Notices:
                                    Credit Acceptance Corporation
                                    25505 W. 12 Mile Road, Suite 3000
                                    Southfield, Michigan 48034
                                    Fax No.: 248-827-8542
                                    Telephone No.: 248-353-2700
                                    Attention: Doug Busk



                                    AUTO FUNDING AMERICA OF NEVADA INC.
                                    CREDIT ACCEPTANCE CORPORATION LIFE
                                    INSURANCE COMPANY
                                    BUYERS VEHICLE PROTECTION PLAN, INC.
                                    CAC LEASING, INC.
                                    VEHICLE REMARKETING SERVICES, INC.
                                    CREDIT ACCEPTANCE CORPORATION OF
                                    NEVADA, INC.


                                    By: /s/ Douglas W. Busk
                                    Name: Douglas W. Busk
                                    Title: Treasurer
                                    Address for Notices:
                                    c/o Credit Acceptance Corporation
                                    25505 W. 12 Mile Road, Suite 3000
                                    Southfield, Michigan 48034
                                    Fax No.: 248-827-8542
                                    Telephone No.: 248-353-2700
                                    Attention: Doug Busk


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<PAGE>


                                    COLLATERAL AGENT:

                                    COMERICA BANK as Collateral Agent


                                    By: /s/ Caryn Dorfman
                                    Name: Caryn Dorfman
                                    Title: Assistant Vice President

                                    Address for Notices:
                                    Metropolitan Loans D
                                    One Detroit Center, 6th Floor
                                    500 Woodward Avenue
                                    Detroit, Michigan 48226
                                    Fax No.: 313/222-3503
                                    Telephone No.:313/222-4865
                                    Attention: Caryn Dorfman




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<PAGE>
                                  ATTACHMENT 1
                                   SCHEDULE D
                                       TO
                               SECURITY AGREEMENT

                                 Pledged Shares
<TABLE>
<CAPTION>
---------------------------------------------------------------------------------------------------------------

                                                                           Pledged Shares as %
                                                                           of Total Shares       Total Shares
                                                         No. of Pledged    Issued and            Issued and
Issuer                    Owner        Certificate No.   Shares            Outstanding           Outstanding
---------------------------------------------------------------------------------------------------------------
<S>                       <C>          <C>               <C>               <C>                   <C>
Auto Funding America of   Company      1                 1,000             100%                  1,000
Nevada, Inc.
---------------------------------------------------------------------------------------------------------------
Buyers Vehicle            Company      1                 1,000             100%                  1,000
Protection Plan, Inc.
---------------------------------------------------------------------------------------------------------------

CAC Leasing, Inc.         Company      1                 1,000             100%                  1,000
---------------------------------------------------------------------------------------------------------------

Vehicle Remarketing       Company      1                 10                100%                  10
Services, Inc.
---------------------------------------------------------------------------------------------------------------

Credit Acceptance         Company      2                 100,000           100%                  100,000
Corporation Life
Insurance Company
---------------------------------------------------------------------------------------------------------------

Credit Acceptance         Company      1                 1,000             100%                  1,000
Corporation of Nevada,
Inc.
---------------------------------------------------------------------------------------------------------------

CAC of Canada Limited     Company      3                 487,565           65%                   750,100
---------------------------------------------------------------------------------------------------------------

The entire
Non-Specified Interest
of Company in the
Titling Subsidiary,
evidenced by
Certificate No. 1
under the Titling
Subsidiary
Agreements
---------------------------------------------------------------------------------------------------------------
</TABLE>










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