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EGR Modulator

  1. Remove vacuum hoses from modulator. Plug modulator ports No. 2 and 3. See Fig 1 . Blow into port No. 4. Air should pass from filter.
  2. Connect hand-held vacuum pump to port No. 5. Plug ports No. 2 and 3. Blow air into port No. 4. Vacuum pump should not obtain vacuum. Replace EGR modulator if defective.
Fig 1: Identifying EGR Modulator Ports
G121717Courtesy of GENERAL MOTORS CORP.
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