UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, DC 20549-1004

FORM 10-Q/ A

(Amendment No. 1)

QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15 (d)

OF THE SECURITIES EXCHANGE ACT OF 1934

For the quarterly period ended June 30, 2004

OR

TRANSITION REPORT PURSUANT TO SECTION 13 OF

THE SECURITIES EXCHANGE ACT OF 1934

For the transition period from                                      to                                     .

Commission file No. 1-14787

DELPHI CORPORATION

(Exact name of registrant as specified in its charter)

(248) 813-2000

(Registrant’s telephone number, including area code)

      Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15 (d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days.     Yes o  No þ.

      Indicate by check mark whether the registrant is an accelerated filer (as defined in Rule 12b-2 of the Exchange Act).     Yes þ  No o.

      As of June 30, 2004 there were 561,192,179 outstanding shares of the registrant’s $0.01 par value common stock.

Explanatory Note

      This Amendment No. 1 on Form 10-Q/ A (“Form 10-Q/ A”) to our Quarterly Report on Form 10-Q for the quarterly period ended June 30, 2004, initially filed with the Securities and Exchange Commission (the “SEC”) on July 16, 2004 (the “Original Filing”), is being filed to reflect the restatement of our consolidated balance sheets at June 30, 2004 and December 31, 2003, our consolidated statements of income, and our consolidated statements of cash flows for each of the three months and six months ended June 30, 2004 and June 30, 2003, and the notes related thereto. The decision to restate Delphi’s consolidated financial statements was previously announced in our Current Report on Form 8-K filed with the SEC on March 4, 2005. The decision to restate was based on the findings of an internal investigation conducted by Delphi’s Audit Committee of the Board of Directors. For a more detailed description of these restatements, see Note 2 Restatement to the accompanying consolidated financial statements contained in this Form 10-Q/ A.

      Although this Form 10-Q/ A sets forth the Original Filing in its entirety, this Form 10-Q/ A only amends and restates Items 1, 2 and 4 of Part I, and Item 6 of Part II of the Original Filing, in each case, solely as a result of, and to reflect the restatement, and no other information in the Original Filing is amended hereby. Accordingly, the items have not been updated to reflect other events occurring after the Original Filing or to modify or update those disclosures affected by subsequent events.

      Except for the foregoing amended information, this Form 10-Q/ A continues to describe conditions as of the date of the Original Filing, and we have not updated the disclosures contained herein to reflect events that occurred at a later date. Other events occurring after the filing of the Original Filing or other disclosures necessary to reflect subsequent events have been or will be addressed in either our amended Quarterly Report on Form 10-Q/ A for the quarterly period ended March 31, 2004, Form 10-Q for the quarterly period ended September 30, 2004 and/ or by our Annual Report on Form 10-K for the year ended December 31, 2004, which are being filed concurrently with the filing of this Form 10-Q/ A, or other reports filed with the SEC subsequent to the date of this filing.

DELPHI CORPORATION

INDEX

PART I. FINANCIAL INFORMATION

ITEM 1. FINANCIAL STATEMENTS

DELPHI CORPORATION

CONSOLIDATED STATEMENTS OF INCOME (Unaudited)

See notes to consolidated financial statements.

DELPHI CORPORATION

CONSOLIDATED BALANCE SHEETS

See notes to consolidated financial statements.

DELPHI CORPORATION

CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited)

See notes to consolidated financial statements.

DELPHI CORPORATION

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (Unaudited)

      General — Delphi Corporation (“Delphi”) is a world-leading supplier of vehicle electronics, transportation components, integrated systems and modules and other electronic technology. The consolidated financial statements and notes thereto included in this report should be read in conjunction with our consolidated financial statements and notes thereto included in our 2004 Annual Report on Form 10-K filed with the Securities and Exchange Commission. The consolidated financial statements include the accounts of Delphi and its subsidiaries.

      All significant intercompany transactions and balances between consolidated Delphi businesses have been eliminated. In the opinion of management, all adjustments, consisting of only normal recurring items, which are necessary for a fair presentation have been included. The results for interim periods are not necessarily indicative of results which may be expected from any other interim period or for the full year and may not necessarily reflect the consolidated results of operations, financial position and cash flows of Delphi in the future.

      Adoption of FSP 106-2 — On May 19, 2004, the FASB issued FASB Staff Position (“FSP”) 106-2 “Accounting and Disclosure Requirements Relating to the Medicare Prescription Drug, Improvement and Modernization Act of 2003,” providing additional guidance relating to the accounting for the effects of the “Medicare Prescription Drug, Improvement and Modernization Act of 2003,” (the “Act”) enacted on December 8, 2003. Because Delphi’s normal measurement date for other post retirement benefit obligations is September 30 of each year, FSP 106-2 requires a one-quarter lag from the remeasurement date (December 8, 2003) before applying the effects of the Act. In connection with the adoption of the provisions of FSP 106-2 in the third quarter of 2004, Delphi retroactively reduced net income for the three months ended March 31, 2004 by $7 million and increased net income for the three months ended June 30, 2004 by $2 million. The adoption of FSP 106-2 did not impact net income for any period in 2003.

      Earnings Per Share — Basic earnings per share amounts were computed using weighted average shares outstanding for each respective period. Diluted earnings per share also reflect the weighted average impact from the date of issuance of all potentially dilutive securities, unless inclusion would not have had a dilutive effect.

      Actual weighted average shares outstanding used in calculating basic and diluted earnings per share were:

      Securities excluded from the computation of diluted earnings per share:

      The Board of Directors declared a dividend on Delphi common stock of $0.07 per share on June 22, 2004, which was paid on August 3, 2004 to holders of record on July 6, 2004. The dividend declared on March 1, 2004 was paid on April 12, 2004.

      Stock-Based Compensation — As allowed under Statement of Financial Accounting Standards (“SFAS”) No. 123, “Accounting for Stock-Based Compensation,” Delphi accounts for a majority of its stock-based compensation using the intrinsic value method in accordance with Accounting Principles Board Opinion No. 25, “Accounting for Stock Issued to Employees,” and related interpretations. Stock options granted during the three months ended June 30, 2004 were exercisable at prices equal to the fair market value of Delphi common stock on the dates the options were granted; accordingly, no compensation expense has been recognized for the stock options granted.

      If we accounted for all stock-based compensation using the fair value recognition provisions of SFAS No. 123 and related amendments, our net income and basic and diluted earnings per share would have been as follows:

      In May 2004, Delphi’s existing outstanding equity compensation plans expired and shareholders approved a new equity compensation plan, which provides for issuances of up to 36.5 million shares of

common stock. During the second quarter, we issued approximately 4.5 million restricted stock units and approximately 6.8 million options. As of June 30, 2004, there are approximately 25.2 million shares available for future grants under this plan.

      Reclassifications — Reclassifications have been made to present minority interest and equity income separately in the Consolidated Statements of Income, which also resulted in a reclassification of income tax expense. Intangible assets and minority interest have been reclassified for separate presentation on the Consolidated Balance Sheets. Equity income has also been reclassified in the Consolidated Statements of Cash Flows.

      These consolidated financial statements have been restated in order to reflect adjustments to the Company’s quarterly financial information originally reported on Form 10-Q for the three and six months ended June 30, 2004. The restatement also affects the three and six months ended June 30, 2003. Amounts disclosed in this note that are as of or for the periods ended June 30, 2004, or June 30, 2003 are all unaudited. The restated financial statements have been prepared by management and reflect all adjustments known to management.

      Refer to Note 2 Restatement and Item 6. Selected Financial Data in the 2004 Form 10-K, which is being filed concurrently with this Form 10-Q/ A, for further discussion of this restatement including the adjustments recorded in the 2003 and 2002 annual periods and quarterly periods of 2004 and 2003. This note discusses the restatement adjustments included in the 2004 Form 10-K as they relate to the second quarters of 2004 and 2003.

      The decision to restate originally reported financial information was based on the results of an independent investigation conducted by the Audit Committee of Delphi’s Board of Directors. The investigation was initiated in response to a Securities and Exchange Commission (the “SEC”) inquiry regarding the accounting for certain transactions with suppliers of information technology services in 2001. The transactions under the Audit Committee internal review included rebates, credits or other lump sum payments received from suppliers or paid to customers from 1999 to 2004. In the course of the investigation, the Audit Committee also examined Delphi’s accounting for transactions involving the disposition of indirect material and inventory and certain other transactions. Based on an assessment of the impact of the adjustments, management and the Audit Committee determined that restatement of Delphi’s originally issued consolidated financial statements was required.

      The following table summarizes the impact of these adjustments to Delphi’s originally reported net income for the three and six months ended June 30, 2004 and June 30, 2003. These adjustments impacted originally reported sales, costs of sales, selling, administrative and other expenses and income tax expense on the statement of operations.

      The following represent the adjustments included in the restatement (all amounts are pre-tax unless otherwise noted):

      The following is a summary of the impact of the restatement on the originally issued consolidated statement of operations, consolidated balance sheets and consolidated statement of cash flows included in this filing.

CONSOLIDATED STATEMENTS OF INCOME

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED STATEMENTS OF CASH FLOWS

      Certain amounts in the notes to the consolidated financial statements have been restated to reflect the restatement adjustments described above.

      In the third quarter of 2003, Delphi approved plans to reduce our U.S. hourly workforce by up to approximately 5,000 employees, our U.S. salaried workforce by approximately 500 employees, and our non-U.S. workforce by approximately 3,000 employees. Based on progress to date, we now anticipate 500 to 1,000 additional hourly employees will leave Delphi bringing our total attrition to U.S. hourly 5,500 to 6,000. Our plans entail reductions to our workforce through a variety of methods including regular attrition and retirements, and voluntary and involuntary separations, as applicable. Under certain elements of the plans, the International Union, United Automobile, Aerospace, and Agricultural Implement Workers of America (“UAW”) hourly employees may return (“flowback”) to General Motors (“GM”). As required under generally accepted accounting principles, we record the costs associated with the flowback to GM as the employees accept the offer to exit Delphi. Including $15 million of costs for additional U.S. hourly employees, we expect to incur total charges related to these initiatives of approximately $765 million (pre-tax) through December 31, 2004, of which $46 million ($14 million in cost of sales and $32 million in employee and product line charges) and $136 million ($66 million in cost of sales and $70 million in employee and product line charges) were recorded during the three and six months ended June 30, 2004, respectively, and $561 million was recorded in 2003. The charges to cost of sales include costs for employees who are idled prior to separation. We expect to incur the remaining estimated charges of $68 million (pre-tax) related to the hourly employee reductions and other structural cost initiatives during the remainder of 2004, including $19 million in the DPTI sector, $20 million in the EES sector and $27 million in the AHG sector. Plans to separate U.S. salaried and non-U.S. salaried employees under a variety of programs were substantially completed during the first quarter of 2004. During the second quarter of 2004, approximately 1,175 U.S. hourly employees flowed back to GM or retired. Cumulatively through June 30, 2004, approximately 4,925 U.S. hourly employees have left the company pursuant to these plans.

      Following is a summary of the activity in the employee and product line reserve (in millions):

      The estimated cash impact of these initiatives is approximately $0.7 billion, of which $88 million and $281 million was paid during the three and six months ended June 30, 2004, respectively, and $176 million was paid in 2003. We expect that up to $0.2 billion will be paid in subsequent quarters in 2004 and the remainder in 2005.

      We maintained a $600 million revolving accounts receivable securitization program in the U.S. (“U.S. Facility Program”) in 2004. Under this U.S. Facility Program, we sell a portion of our U.S. originated trade receivables to Delphi Receivables LLC (“DR”), a wholly-owned consolidated special purpose entity. DR may then sell, on a non-recourse basis (subject to certain limited exceptions), an undivided interest in the receivables to asset-backed, multi-seller commercial paper conduits (“Conduits”). Neither the Conduits nor the associated banks are related to Delphi or DR. The Conduits typically finance the purchases through the issuance of A1/P1 rated commercial paper. In the event that the Conduits become unable to or otherwise elect not to issue commercial paper and make purchases, the associated banks are obligated to make the purchases. The sale of the undivided interest in the receivables from DR to the Conduits is accounted for as a sale under the provisions of SFAS No. 140, “Accounting for the Transfers and Servicing of Financial Assets and Extinguishments of Liabilities” (“SFAS 140”). When DR sells an undivided interest to the Conduits, DR retains the remaining undivided interest. The value of the undivided interest sold to the Conduits is excluded from our consolidated balance sheet thereby reducing our accounts receivable. The value of the retained interest in receivables held by DR, which may include eligible undivided interests that we elect not to sell, is shown separately on our consolidated balance sheet and therefore is not included in our accounts receivable. As of June 30, 2004, the retained interest in receivables, net was $586 million. We assess the recoverability of the retained interest on a quarterly basis and adjust to the carrying value as necessary.

      At the time DR sold the undivided interest to the Conduits the sale was recorded at fair value with the difference between the carrying amount and fair value of the assets sold included in operating income as a loss on sale. This difference between carrying value and fair value is principally the estimated discount inherent in the U.S. Facility Program, which reflects the borrowing costs as well as fees and expenses of the Conduits (approximately 1.4% to 1.6%), and the length of time the receivables are expected to be outstanding. The loss on sale was approximately $1.7 million and $2.4 million for the three and six months ended June 30, 2004, respectively. Additionally, we perform collections and administrative functions on the receivables sold similar to the procedures we use for collecting all of our receivables, including receivables

that are not sold under the U.S. Facility Program. We can elect to keep the collections and sell additional receivables in exchange; or, we can transfer the cash collections to the Conduits thereby reducing the amount of sales of undivided interests to the Conduits. The nature of the collection and administrative activities and the terms of the U.S. Facility Program do not result in the recognition of a servicing asset or liability under the provisions of SFAS 140 because the benefits of servicing are just adequate to compensate us for our servicing responsibilities.

      The U.S. Facility Program, which is among Delphi, DR, the Conduits, the sponsoring banks and their agents, was renewed on March 29, 2004 and extended through March 24, 2005. The program was increased from $500 million to $600 million in March 2004 and can be extended for additional 364-day periods based upon the mutual agreement of the parties. The U.S. Facility Program contains a financial covenant and certain other covenants similar to our revolving credit facilities that, if not met, could result in a termination of the program. At June 30, 2004, we were in compliance with all such covenants.

      The table below summarizes certain cash flows received from and paid to the Conduits under the revolving U.S. Facility Program during the three and six months ended June 30, 2004:

      In November 2003, we entered into a €330 million ($400 million at June 30, 2004 currency exchange rates) and £30 million ($54 million at June 30, 2004 currency exchange rates) trade receivable securitization program for certain of our European accounts receivable. Accounts receivable transferred under this program are accounted for as short-term debt. As of June 30, 2004 and 2003, we had no significant accounts receivable transferred under this program. The program can be extended based upon the mutual agreement of the parties. Additionally, the European program contains a financial covenant and certain other covenants similar to our revolving credit facilities that, if not met, could result in a termination of the agreement. At June 30, 2004 and 2003, we were in compliance with all such covenants.

      The program was renewed in December 2004 at €225 million ($273 million at June 30, 2004 currency exchange rates) and £10 million ($18 million at June 30, 2004 currency exchange rates) and currently expires on December 1, 2005. The program can be extended upon the mutual agreement of the parties. Further, in March 2005 Delphi amended the European trade receivables securitization program to conform the leverage ratio financial covenant consistent with the amended credit facilities’ covenant and amended other procedural terms.

      We recognize expected warranty costs for products sold principally at the time of sale of the product based on management estimates of the amount that will eventually be required to settle such obligations.

These accruals are based on several factors including past experience, production changes, industry developments and various other considerations. Our estimates are adjusted from time to time based on facts and circumstances that impact the status of existing claims. The table below summarizes the activity in the product warranty liability for the six months ended June 30, 2004.

      Approximately $194 million and $165 million of the warranty accrual balance as of June 30, 2004 and December 31, 2003, respectively, is included in accrued liabilities in the accompanying consolidated balance sheet. The remainder of the warranty accrual balance is included in other long-term liabilities.

      Pension plans covering unionized employees in the U.S. generally provide benefits of negotiated stated amounts for each year of service, as well as supplemental benefits for employees who qualify for retirement before normal retirement age. The benefits provided by the plans covering U.S. salaried employees are generally based on years of service and salary history. Certain Delphi employees also participate in nonqualified pension plans covering executives, which are not funded. Such plans are based on targeted wage replacement percentages, and are generally not significant to Delphi. Delphi’s funding policy with respect to its qualified plans is to contribute at least the minimum amounts required by applicable laws and regulations.

      The 2004 and 2003 amounts shown below reflect the defined benefit pension and other postretirement benefit expense for the three and six months ended June 30 for each year for U.S. salaried and hourly employees:

      During each of the six months ended June 30, 2004 and June 30, 2003, Delphi contributed $0.6 billion to its U.S. pension plans. Certain of Delphi’s non-U.S. subsidiaries also sponsor defined benefit pension plans. The pension expense for these locations for the three months ended June 30, 2004 and 2003

was $19 million and $16 million, respectively, and for the six months ended June 30, 2004 and 2003 was $40 million and $32 million, respectively.

      Other postretirement benefits expense during the three and six months ended June 30, 2004 increased by $20 million and $53 million, respectively, compared to the comparable periods in 2003. The total impact of the Act on our actuarial liability was $0.5 billion and is being accounted for as an actuarial gain will be amortized as a reduction of our periodic expense and balance sheet liability over the next ten to twelve years.

      Effective March 1, 2005 Delphi amended its health care benefits plan for salaried retirees. Under this plan amendment effective January 1, 2007, Delphi reduced its obligations to current salaried active employees, all current retirees and surviving spouses who are retired and are eligible for Medicare coverage. Based on a March 1, 2005 remeasurement date, the expected impact of this amendment will be a decrease in the OPEB liability of $0.8 billion and a decrease in 2005 expense of $72 million. As SFAS No. 106 “Employers’ Accounting for Postretirement Benefits Other than Pensions” requires a one-quarter lag from the remeasurement date before applying the effects of the plan amendment, income statement recognition of the plan amendment will begin in June 2005.

      Delphi is exposed to market risk, such as fluctuations in foreign currency exchange rates, commodity prices and changes in interest rates, which may result in cash flow risks. To manage the volatility relating to these exposures, we aggregate the exposures on a consolidated basis to take advantage of natural offsets. For exposures that are not offset within our operations, we enter into various derivative transactions pursuant to our risk management policies. Designation is performed on a transaction basis to support hedge accounting. The changes in fair value of these hedging instruments are offset in part or in whole by corresponding changes in the fair value or cash flows of the underlying exposures being hedged. We assess the initial and ongoing effectiveness of our hedging relationships in accordance with our documented policy. We do not hold or issue derivative financial instruments for trading purposes.

      The fair value of derivative financial instruments as of June 30, 2004 and December 31, 2003 included current and non-current assets of $38 million and $58 million, respectively and current and non-current liabilities of $17 million and $55 million, respectively. Gains and losses on derivatives qualifying as cash flow hedges are recorded in other comprehensive income (“OCI”) to the extent that hedges are effective until the underlying transactions are recognized in earnings. Net gains included in OCI as of June 30, 2004, were $27 million after-tax ($42 million pre-tax). Of this pre-tax total, a gain of approximately $37 million is expected to be included in cost of sales within the next 12 months and a loss of approximately $1 million is expected to be included in subsequent periods. A loss of approximately $2 million is expected to be included in depreciation and amortization expense over the lives of the related fixed assets and a gain of approximately $8 million is expected to be included in interest expense over the term of the related debt. The unrealized amounts in OCI will fluctuate based on changes in the fair value of open contracts at each reporting period. The amount included in cost of sales related to hedge ineffectiveness and the time value of options was not material.

      Changes in stockholders’ equity for the six months ended June 30, 2004 were: