R E P O R T O F I N D E P E N D E N T R E G I S T E R E D P U B L I C A C C O U N T I N G F I R M O N T H E C O M P A N Y ’ S I N T E R N A L C O N T R O L O V E R F I N A N C I A L R E P O R T I N G  The Board of Directors and Stockholders of PACCAR Inc We have audited PACCAR Inc’s internal control over financial reporting as of December 31, 2011, based on criteria  established in Internal Control—Integrated Framework issued by the Committee of Sponsoring Organizations of  the Treadway Commission (the COSO criteria). PACCAR Inc’s management is responsible for maintaining effective  internal control over financial reporting, and for its assessment of the effectiveness of internal control over  financial reporting included in the accompanying Management’s Report on Internal Control Over Financial  Reporting. Our responsibility is to express an opinion on the company’s internal control over financial reporting  based on our audit.  We conducted our audit in accordance with the standards of the Public Company Accounting Oversight Board  (United States). Those standards require that we plan and perform the audit to obtain reasonable assurance about  whether effective internal control over financial reporting was maintained in all material respects. Our audit  included obtaining an understanding of internal control over financial reporting, assessing the risk that a material  weakness exists, testing and evaluating the design and operating effectiveness of internal control based on the  assessed risk, and performing such other procedures as we considered necessary in the circumstances. We believe  that our audit provides a reasonable basis for our opinion. A company’s internal control over financial reporting is a process designed to provide reasonable assurance  regarding the reliability of financial reporting and the preparation of financial statements for external purposes in  accordance with generally accepted accounting principles. A company’s internal control over financial reporting  includes those policies and procedures that (1) pertain to the maintenance of records that, in reasonable detail,  accurately and fairly reflect the transactions and dispositions of the assets of the company; (2) provide reasonable  assurance that transactions are recorded as necessary to permit preparation of financial statements in accordance  with generally accepted accounting principles, and that receipts and expenditures of the company are being made  only in accordance with authorizations of management and directors of the company; and (3) provide reasonable  assurance regarding prevention or timely detection of unauthorized acquisition, use, or disposition of the  company’s assets that could have a material effect on the financial statements. Because of its inherent limitations, internal control over financial reporting may not prevent or detect  misstatements. Also, projections of any evaluation of effectiveness to future periods are subject to the risk that  controls may become inadequate because of changes in conditions, or that the degree of compliance with the  policies or procedures may deteriorate. In our opinion, PACCAR Inc maintained, in all material respects, effective internal control over financial  reporting as of December 31, 2011, based on the COSO criteria. We also have audited, in accordance with the standards of the Public Company Accounting Oversight Board  (United States), the consolidated balance sheets of PACCAR Inc as of December 31, 2011 and 2010, and the related  consolidated statements of income, comprehensive income, stockholders’ equity, and cash flows for each of the three  years in the period ended December 31, 2011 and our report dated February 29, 2012 expressed an unqualified  opinion thereon. Seattle, Washington February 29, 2012