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Diagnosis & Repair (Using OBD-II Scan Tester)

  1. Disconnect EGR temperature sensor. Sensor is located on manifold between EGR valve and throttle body. Using ohmmeter, measure resistance between sensor terminals. If resistance is 600 k/ohms or less, go to next step. If resistance is more than 600 k/ohms, inspect sensor. See SYSTEM/COMPONENT TESTS . Replace as necessary.
  2. Turn ignition on. Using DVOM, measure voltage between sensor wiring 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 connector. Measure voltage between terminal No. 14 (Green/Red wire) at ECM E6 connector and No. 22 (Brown wire) at ECM E7 connector. See Figure. If voltage is 4.5-5.5 volts, inspect circuits between EGR tempe rature sensor and ECM for open. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. If voltage is not 4.4-5.5 volts, replace ECM and retest.
  4. Inspect all EGR system vacuum hoses. Replace as necessary. Access ECM behind glove box. Ensure ignition is off. Disconnect ECM E6 connector. Turn ignition on. Connect a jumper wire between ground and terminal No. 12 (Black/White wire) at ECM E6 connector.
  5. With jumper wire connected, Vacuum Switching Valve (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). If valve does not operate correctly, go to next step.
  6. Turn ignition off. Remove EGR VSV. Using ohmmeter, measure resistance between valve terminals. Resistance should be 33-39 ohms at 68°F (20°C). Measure resistance between each terminal and body of valve. Resistance should be infinite. Replace VSV as necessary. If resistance is as specified, go to next step.
  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 th rough valve. Replace as necessary.
  8. If valve meets all specifications in steps 6) and 7), inspect circuits between EGR VSV and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary.
  9. Inspect EGR vacuum modulator. See SYSTEM/COMPONENT TESTS article. Replace as necessary. If vacuum modulator is okay, inspect EGR valve. See SYSTEM/COMPONENT TESTS article. Replace as necessary.
  10. Disconnect EGR temperature sensor connector. Start engine. Ensure engine is at normal operating temperature. Disconnect EGR VSV. Run engine at 4000 RPM for 3 minutes and measure resistance between EGR temperature sensor terminals. If resistance is 4300 ohms or less, replace ECM and retest. If resistance is more than 4300 ohms, replace sensor.
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