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Pulse Width Modulated EGR Valve

  1. Check vacuum lines for leaks and electrical connectors for proper installation. Place transmission in Park or Neutral. With engine at normal operating temperature and engine idling, push up on underside of EGR valve diaphragm. Engine RPM should drop. If engine RPM does not drop, clean EGR valve and passages.
  2. Check for EGR valve diaphragm movement with engine RPM change from 2000 RPM to idle. EGR valve diaphragm should not change. If EGR valve diaphragm moves with RPM change, check Park/Neutral switch for open circuit or misadjustment. If EGR valve diaphragm does not move, disconnect ALDL "test" connector and ground test terminal. If EGR valve diaphragm moves, EGR valve is functioning properly.
  3. If EGR valve diaphragm still does not move, stop engine and disconnect EGR solenoid connector. Connect 12-volt test light between EGR solenoid connector terminals. Turn ignition on and ground ALDL "test" terminal. Test light should flash repeatedly.
  4. If test light flashes, check for vacuum to EGR solenoid at 2000-3000 RPM. If engine does not use a vacuum regulator, there should be at least 7 in. Hg vacuum at solenoid. If engine is equipped with a vacuum regulator, there should be 2-10 in. Hg vacuum.
  5. If vacuum is greater than 10 in. Hg, replace regulator. If vacuum is less than 2 in. Hg, vacuum at solenoid is okay and check EGR solenoid connections and/or faulty EGR solenoid. See appropriate C-7 CHART in the COMPUTERIZED ENGINE CONTROLS section for further diagnosis.
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