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EXHIBIT 31.2

CERTIFICATION OF CHIEF FINANCIAL OFFICER

I, Don P. Duffy, certify that:



|1. |  | I have reviewed this annual report on Form 10-K of Onyx Acceptance Corporation;
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|2. |  | Based on my knowledge, this annual report does not contain any untrue statement of a material
fact or omit to state a material fact necessary to make the statements made, in light
of the circumstances under which such statements were made, not misleading with
respect to the period covered by this annual report;
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|3. |  | Based on my knowledge, the financial statements, and other financial information
included in this annual report, fairly present in all material respects the financial
condition, results of operations and cash flows of the registrant as of, and for, the
periods presented in this annual report;
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|4. |  | The registrants other certifying officer and I are responsible for establishing and
maintaining disclosure controls and procedures (as defined in Exchange Act Rules
13a-15(e) and 15d-15(e)) for the registrant and have:
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| | a) |  | designed such disclosure
controls and procedures,
or caused such disclosure
controls and procedures to
be designed under our
supervision, to ensure
that material information
relating to the
registrant, including its
consolidated subsidiaries,
is made known to us by
others within those
entities, particularly
during the period in which
this annual report is being
prepared;
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| | b) |  | evaluated the
effectiveness of the
registrants disclosure
controls and procedures
and presented in this
annual report our conclusions
about the effectiveness of
the disclosure controls
and procedures, as of the
end of the period covered
by this annual report based on
such evaluation; and
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| | c) |  | disclosed in this annual report
any change in the
registrants internal
control over financial
reporting that occurred
during the registrants
most recent fiscal quarter
that has materially
affected, or is reasonably
likely to materially
affect, the registrants
internal control over
financial reporting; and
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|5. |  | The registrants other certifying officer and I have disclosed, based on our
most recent evaluation of internal control over financial reporting, to the
registrants auditors and the audit committee of the registrants board of
directors (or persons performing the equivalent functions):
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| | a) |  | all significant deficiencies and material
weaknesses in the design or operation of
internal control over financial reporting which
are reasonably likely to adversely affect the
registrants ability to record, process,
summarize and report financial information; and
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| | b) |  | any fraud, whether or not material, that
involves management or other employees who have
a significant role in the registrants internal
control over financial reporting.
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Date: March 30, 2004

/s/ DON P. DUFFYDon P. Duffy Executive Vice President,
CFO and Principal Financial Officer