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Diagnosis & Repair (OBD-II Scan Tester ONLY)

  1. Disconnect EGR gas temperature sensor. Sensor is located on manifold between EGR valve and throttle body. Using ohmmeter, measure resistance between sensor terminals. If resistance is 600,000 ohms or less, go to next step. If resistance is NOT 600,000 ohms or less, inspect sensor. See SYSTEM/COMPONENT TESTS article. Replace as needed.
  2. Turn ignition on. Using DVOM, measure voltage between sensor harness connector terminals. If voltage is 4.5-5.5 volts, go to step  4. If voltage is NOT 4.4-5.5 volts, go to next step.
  3. Access ECM behind glove box. Using DVOM, backprobe harness connector. Measure voltage between ECM connector "E6" terminal No. 14 (THG) and connector "E7" terminal No. 22 (E2). See Figure. If voltage is 4.5-5.5 volts, inspect circuits between EGR gas temperature sensor and ECM for open. See WIRING DIAGRAMS article. Repair as needed. If voltage is NOT 4.4-5.5 volts, replace ECM and retest.
  4. Inspect all EGR system vacuum hoses. Replace as needed. Check operation of EGR Vacuum Switching Valve (VSV). Access ECM behind glove box. Ensure ignition is off. Disconnect ECM harness connector "E6". Turn ignition on. Using jumper wire, connect ECM connector "E6" terminal No. 12 (EGR) to ground.
  5. VSV is located under intake plenum cover. With jumper wire connected, VSV is on. Air should exhaust through filter on end of valve. See Figure. Disconnect jumper wire. Air should pass through valve. If valve operates correctly, go to step  9.
  6. If valve does operate correctly, turn ignition off. Remove EGR VSV. Using ohmmeter, measure resistance between valve terminals. Resistance should be 26-46 ohms at 68°F (20°C). Measure resistance between each terminal and body of valve. Resistance should be infinite. Replace VSV as needed.
  7. Check VSV operation. Apply battery voltage to valve terminals. Air should exhaust from small filter on end of valve. See Figure. Remove battery voltage from valve terminals. Air should pass through valve. Replace as needed.
  8. If valve meets all specifications in steps  6 and  7 , inspect circuits between EGR VSV and ECM. See wiring diagram in WIRING DIAGRAMS article. Repair as needed.
  9. Inspect EGR vacuum modulator. See procedures in SYSTEM/COMPONENT TESTS article. Replace as needed. Inspect EGR valve. See SYSTEM/COMPONENT TESTS article. Replace as needed.
  10. Inspect EGR gas temperature sensor. Start and run engine. Select active test mode on scan tester (EGR system ON). Run engine at 4000 RPM for 3 minutes. Monitor EGR gas temperature. Temperature should be 284°F (140°C) or more.
  11. If temperature is NOT within specification, replace sensor. If temperature is within specification, replace ECM and retest.
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