<PAGE>
                                                                 Exhibit 10.1(b)

                    SECOND AMENDMENT TO THE CREDIT AGREEMENT

      SECOND AMENDMENT, dated as of December 3, 2003 (the "Amendment"), to the
Credit Agreement, dated as of January 31, 2003, as amended by the First
Amendment dated as of March 19, 2003 (the "Credit Agreement"), among VIASYSTEMS
GROUP, INC. ("Holdings"), VIASYSTEMS, INC. (the "Borrower"), the several banks
and other financial institutions from time to time parties thereto (the
"Lenders") and JPMORGAN CHASE BANK, as administrative agent for the Lenders (in
such capacity, the "Administrative Agent").

                              W I T N E S S E T H:

      WHEREAS, Holdings, the Borrower, the Lenders and the Administrative Agent
are parties to the Credit Agreement;

      WHEREAS, the Borrower has requested that the Lenders agree to amend the
Credit Agreement as provided herein; and

      WHEREAS, the parties hereto are willing to agree to such amendment, but
only upon the terms and subject to the conditions set forth herein;

      NOW THEREFORE, in consideration of the premises and the mutual covenants
hereinafter set forth, the parties hereto hereby agree as follows:

      1. Defined Terms. Unless otherwise defined herein, capitalized terms that
are defined in the Credit Agreement are used herein as therein defined.

      2. Amendment to Subsection 1.1--Consolidated EBITDA. The definition of
"Consolidated EBITDA" contained in subsection 1.1 of the Credit Agreement is
hereby amended by (a) adding the following new subclause (xi) to the end of
clause (A) thereof:

      "and (xi) any Permitted Management Fees accrued but not paid in cash"

and (b) adding the following new subclause (iii) to the end of clause (B)
thereof:

      "and (iii) any cash payments in respect of accrued Permitted Management
      Fees referred to in clause (A)(xi) above to the extent not already
      reflected as a charge in the statement of such Net Income for such period"

      3. Amendment to Subsection 1.1--Consolidated Total Debt. The definition of
"Consolidated Total Debt" contained in subsection 1.1 of the Credit Agreement is
hereby amended in its entirety to read as follows:

      "Consolidated Total Debt": at a particular date, with respect to the
      Borrower, (a) the aggregate principal amount of Indebtedness under this
      Agreement, Financing Leases, purchase money

<PAGE>

      Indebtedness, and any other Indebtedness for borrowed money of the
      Borrower and its Subsidiaries at such date in conformity with GAAP,
      including unreimbursed drawings in respect of Revolving Letters of Credit
      but excluding undrawn letters of credit and Specified Indebtedness minus
      (b) cash and Cash Equivalents then held by the Borrower and its
      Subsidiaries and not subject to any Lien other than Liens created by the
      Loan Documents.

      4. Amendment to Subsection 1.1--Indebtedness. The definition of
"Indebtedness" contained in subsection 1.1 of the Credit Agreement is hereby
amended by adding the words "and accrued Permitted Management Fees" to the end
of the parenthetical contained in clause (b) thereof.

      5. Amendment to Subsection 1.1--New Definitions. Subsection 1.1 of the
Credit Agreement is hereby amended by adding the following definitions in the
appropriate alphabetical order:

      "Permitted Management Fees": as defined in subsection 11.11.

      "Specified Additional Senior Subordinated Indebtedness": any Additional
      Senior Subordinated Indebtedness issued as a condition precedent to the
      effectiveness of the Second Amendment to this Agreement.

      6. Amendment to Subsection 5.3(a). Section 5.3(a) of the Credit Agreement
is hereby amended by adding the following sentence to the end thereof:

      "Notwithstanding the foregoing, if the aggregate gross cash proceeds of
      the Specified Additional Senior Subordinated Indebtedness exceed
      $200,000,000, only 50% of the Net Cash Proceeds associated with such
      excess shall be required to be applied as described in this paragraph
      (a)."

      7. Amendment to Subsection 5.3(c). Subsection 5.3(c) of the Credit
Agreement is hereby amended by changing the percentage "75%" to "50%".

      8. Amendment to Subsection 5.3(d). Subsection 5.3(d) of the Credit
Agreement is hereby amended by adding the following sentence to the end thereof:

      "Notwithstanding the foregoing, Net Cash Proceeds of Specified Additional
      Senior Subordinated Indebtedness may be applied to the installments of the
      Tranche B Term Loans in forward order of maturity."

      9. Amendment to Subsection 9.2. Subsection 9.2 of the Credit Agreement is
hereby amended by replacing each of paragraphs (c) and (d) thereof with the
reference "[INTENTIONALLY OMITTED]".

      10. Amendment to Subsection 11.1(a). The table contained in Subsection
11.1(a) of the Credit Agreement is hereby replaced with the following table:

<TABLE>
<CAPTION>
Calendar Quarter                            Ratio
----------------                            -----
<S>                                     <C>
2003     4th                            1.85 to 1.00
2004     1st                            1.85 to 1.00
         2nd                            1.85 to 1.00
         3rd                            1.85 to 1.00
         4th                            1.85 to 1.00
</TABLE>

                                       2
<PAGE>

<TABLE>
<S>                                     <C>
2005     1st                            1.95 to 1.00
         2nd                            2.05 to 1.00
         3rd                            2.10 to 1.00
         4th                            2.20 to 1.00
2006     1st                            2.30 to 1.00
         2nd                            2.35 to 1.00
         3rd                            2.40 to 1.00
         4th                            2.45 to 1.00
2007     1st                            2.45 to 1.00
         2nd                            2.50 to 1.00
         3rd                            2.50 to 1.00
         4th                            2.55 to 1.00
2008     1st                            2.60 to 1.00
         2nd                            2.60 to 1.00
</TABLE>

      11. Amendment to Subsection 11.1(b). The table contained in Subsection
11.1(b) of the Credit Agreement is hereby replaced with the following table:

<TABLE>
<CAPTION>
Calendar Quarter                   Ratio
----------------                   -----
<S>                             <C>
2003     4th                    6.40 to 1.00
2004     1st                    6.40 to 1.00
         2nd                    6.40 to 1.00
         3rd                    6.40 to 1.00
         4th                    6.25 to 1.00
2005     1st                    6.15 to 1.00
         2nd                    6.00 to 1.00
         3rd                    5.80 to 1.00
         4th                    5.60 to 1.00
2006     1st                    5.40 to 1.00
         2nd                    5.35 to 1.00
         3rd                    5.30 to 1.00
         4th                    5.30 to 1.00
2007     1st                    5.25 to 1.00
         2nd                    5.25 to 1.00
         3rd                    5.25 to 1.00
         4th                    5.20 to 1.00
2008     1st                    5.15 to 1.00
         2nd                    5.15 to 1.00
</TABLE>

      12. Amendment to Subsection 11.1(c). Subsection 11.1(c) of the Credit
Agreement is hereby replaced with the reference "[INTENTIONALLY OMITTED]".

      13. Amendment to Subsection 11.2(n). Subsection 11.2(n) of the Credit
Agreement is hereby amended by inserting the following parenthetical at the end
of clause (i) thereof: "(except as otherwise expressly provided therein)".

      14. Amendment to Subsection 11.8(a). Subsection 11.8(a) of the Credit
Agreement is hereby replaced with the following:

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<PAGE>

      "(a) Make or commit to make any Capital Expenditure except for
      expenditures in the ordinary course of business not exceeding, in the
      aggregate for the Borrower and its Subsidiaries during any fiscal year set
      forth below, the amount set forth opposite such fiscal year below:

<TABLE>
<CAPTION>
Fiscal Year               Amount
-----------               ------
<S>                     <C>
   2003                 $ 92,000,000
   2004                 $103,000,000
   2005                 $112,000,000
   2006                 $117,000,000
   2007                 $117,000,000
   2008                 $ 57,200,000
</TABLE>

      ; provided that 100% of any amount not used in any fiscal year may be
      carried forward only into the next succeeding fiscal year; provided,
      further, that Capital Expenditures made pursuant to this subsection during
      any such fiscal year shall be deemed made, first, in respect of amounts
      permitted for such fiscal year as provided above and, second, in respect
      of amounts carried over from the prior fiscal year pursuant to the proviso
      above."

      15. Amendment to Subsection 11.11. Subsection 11.11 of the Credit
Agreement is hereby amended by replacing the last sentence thereof with the
following sentence:

      "Notwithstanding anything to the contrary in this Agreement (including the
      foregoing clauses (a) and (b)), neither Holdings nor any of its
      Subsidiaries shall accrue or make any payment with respect to any
      management fee (i) to any Affiliate of Holdings or any of its Subsidiaries
      or (ii) to HMTF or any of its Affiliates, except that a management fee may
      be accrued in respect of each fiscal year of the Borrower (commencing with
      the 2003 fiscal year) in an amount equal to the lesser of (x) 2% of
      Consolidated EBITDA for such fiscal year and (y) $1,500,000, which accrual
      shall be deemed earned upon delivery of financial statements for such
      fiscal year in accordance with subsection 10.1(a) and may be paid in cash
      at any time on or after the date on which it has been so earned (such
      management fees, "Permitted Management Fees")."

      16. Amendment to Subsection 11.18. Subsection 11.18 of the Credit
Agreement is hereby amended by changing the amount "$5,000,000" to
"$15,000,000".

      17. Conditions to Effectiveness of this Amendment. This Amendment shall
become effective upon the date when the following conditions are satisfied or
waived (provided that all such conditions must be satisfied on or prior to
January 31, 2004):

            (a) Amendment to Credit Agreement. The Administrative Agent shall
      have received counterparts of this Amendment, duly executed and delivered
      by Holdings and the Borrower;

            (b) Lender Consent Letters. The Administrative Agent shall have
      received Lender Consent Letters (or facsimile transmissions thereof) with
      respect to this Amendment, duly executed and delivered by the Required
      Lenders and by the Majority Facility Lenders in respect of the Tranche B
      Term Facility, consenting to the execution of this Amendment by the
      Administrative Agent;

            (c) Consent Fee. The Administrative Agent shall have received, for
      the account of each Lender that has submitted to the Administrative Agent
      an executed Lender Consent Letter no

                                       4
<PAGE>

      later than 5:00 p.m., New York City time, on December 3, 2003, a consent
      fee in an amount equal to 0.25% of the aggregate amount of each such
      Lender's Assumed Letter of Credit Commitment, Revolving Credit Commitment
      and outstanding principal amount of Tranche B Term Loan (determined after
      giving effect to the mandatory prepayment thereof resulting from the
      issuance of the Specified Additional Senior Subordinated Indebtedness);

            (d) Specified Additional Senior Subordinated Indebtedness. The
      Borrower shall have received aggregate gross cash proceeds from the
      issuance of Additional Senior Subordinated Indebtedness in an amount equal
      to at least $200,000,000;

            (e) No Default. No Default or Event of Default shall have occurred
      and be continuing on such date or after giving effect to the transactions
      (including the amendments to the Credit Agreement) contemplated herein;
      and

            (f) Representations and Warranties. Each of the representations and
      warranties made by the Credit Parties in or pursuant to the Loan Documents
      shall be true and correct in all material respects on and as of the date
      hereof, before and after giving effect to the effectiveness of this
      Amendment, as if made on and as of the date hereof, except to the extent
      such representations and warranties expressly relate to a specific earlier
      date, in which case such representations and warranties were true and
      correct as of such earlier date.

      18. Continuing Effect of the Credit Agreement. This Amendment shall not
constitute an amendment or waiver of any provision of the Credit Agreement not
expressly referred to herein and shall not be construed as an amendment, waiver
or consent to any further or future action on the part of the Credit Parties
that would require an amendment, waiver or consent of the Lenders or
Administrative Agent. Except as expressly amended hereby, the provisions of the
Credit Agreement are and shall remain in full force and effect.

      19. Counterparts. This Amendment may be executed by one or more of the
parties hereto on any number of separate counterparts (including by facsimile or
other suitable means of electronic transmission of a signed counterpart, such as
a pdf file), and all of said counterparts taken together shall be deemed to
constitute one and the same instrument.

      20. GOVERNING LAW. THIS AMENDMENT AND THE RIGHTS AND OBLIGATIONS OF THE
PARTIES UNDER THIS AMENDMENT SHALL BE GOVERNED BY, AND CONSTRUED AND INTERPRETED
IN ACCORDANCE WITH, THE LAW OF THE STATE OF NEW YORK.

            [THE REMAINDER OF THIS PAGE IS INTENTIONALLY LEFT BLANK]

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<PAGE>

      IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be
duly executed and delivered by their proper and duly authorized officers as of
the day and year first above written.

                                           VIASYSTEMS GROUP, INC.

                                           By: /s/ DAVID J. WEBSTER
                                               ---------------------------
                                           Name:  David J. Webster
                                           Title: Senior VP and Secretary

                                           VIASYSTEMS, INC.

                                           By: /s/ DAVID J. WEBSTER
                                               ---------------------------
                                           Name:  David J. Webster
                                           Title: Senior VP and Secretary

                                           JPMORGAN CHASE BANK, as
                                           Administrative Agent

                                           By: /s/ JONATHAN KATZ
                                               ---------------------------
                                           Name:  Jonathan Katz
                                           Title: Vice President

<PAGE>

                              LENDER CONSENT LETTER

                        VIASYSTEMS, INC. CREDIT AGREEMENT
                          DATED AS OF JANUARY 31, 2003

To:   JPMorgan Chase Bank, as Administrative Agent
      270 Park Avenue
      New York, New York 10017

Ladies and Gentlemen:

            Reference is made to the Credit Agreement, dated as of January 31,
2003 (as amended, supplemented or otherwise modified prior to the date hereof,
the "Credit Agreement"), among Viasystems Group, Inc., Viasystems, Inc. (the
"Borrower"), the several banks and other financial institutions from time to
time parties thereto and JPMorgan Chase Bank, as Administrative Agent. Unless
otherwise defined herein, capitalized terms used herein and defined in the
Credit Agreement are so used as so defined.

            The Borrower has requested certain amendments to the Credit
Agreement on the terms described in the Second Amendment to the Credit Agreement
in the form attached hereto as Exhibit A (the "Second Amendment").

            Pursuant to Section 15.1 of the Credit Agreement, the undersigned
Lender hereby consents to the execution by the Administrative Agent of the
Second Amendment.

                                    Very truly yours,

                                    ____________________________________________
                                    (NAME OF LENDER)

                                    By:_________________________________________
                                    Name:
                                    Title:

Dated as of December 3, 2003