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Diagnosis & Repair (Using OBD-II Scan Tool)

  1. Disconnect EGR temperature sensor. Using ohmmeter, measure resistance between sensor terminals. If resistance is 600,000 ohms or less, go to next step. If resistance is more than 600,000 ohms, check 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 4.5-5.5 volts, go to next step.
  3. Access ECM under driver's seat. Using DVOM, backprobe ECM connector. Measure voltage between terminals No. 12 (Brown/White wire) and No. 9 (Brown/Black wire) at ECM E6 connector. See Figure. If voltage is 4.5-5.5 volts, check for open circuit in wiring harness between EGR temperature sensor and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair wiring as necessary. If voltage is not 4.5-5.5 volts, replace ECM and retest.
  4. Check all EGR system vacuum hoses. Replace as necessary. Access ECM under driver's seat. Ensure ignition is off. Disconnect ECM E9 connector. Turn ignition on. Connect a jumper wire between ground and terminal No. 16 (Red/Black wire) at ECM E9 connector.
  5. With jumper wire connected, Vacuum Switching Valve (VSV) is on. Apply air pressure to VSV port "E". Air from port "E" should flow from port "F". See Figure. Disconnect jumper wire. Air from port "E" should flow from filter on end of valve. If valve operates as specified, go to step 8). If valve does not operate as specified, go to next step.
  6. Turn ignition off. Remove EGR VSV. Using ohmmeter, measure resistance between valve terminals. Resistance should be 37-44 ohms at 68°F (20°C). Check continuity between each VSV terminal and body of valve. If continuity exists, replace VSV. If continuity does not exist, go to next step.
  7. Check VSV operation. Apply battery voltage to VSV terminals. Apply air pressure to VSV port "E". Air from port "E" should flow from port "F". See Figure. Remove battery voltage from valve terminals. Air from port "E" should flow from filter on end of valve. Replace VSV as necessary. If VSV operates as specified, check for an open in wiring harness between EGR VSV and ECM. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair wiring as necessary.
  8. Check EGR vacuum modulator. See SYSTEM/COMPONENT TESTS article. Replace as necessary. If modulator is okay, check EGR valve. See SYSTEM/COMPONENT TESTS article. Replace as necessary. If EGR valve is okay, go to next step.
  9. Disconnect EGR temperature sensor connector. Start engine. Ensure engine is at normal operating temperature. Run engine at 3500 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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