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Diagnosis & Repair (Using OBD-II Scan Tool)

  1. Disconnect EGR temperature sensor. Sensor is located on EGR valve assembly. 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 - NON-TURBO article. 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. Connect Check Harness "A" (SST 09990-01000) to ECM. See TEST PREPARATION  under SELF-DIAGNOSTIC SYSTEM. Measure voltage between terminals No. 46 and 65 at Check Harness "B" 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 - NON-TURBO article. Repair wiring as necessary. If voltage is not 4.4-5.5 volts, replace ECM and retest.
  4. Check all EGR system vacuum hoses. Replace as necessary. If vacuum hoses are okay, access ECM behind glove box. Ensure ignition is off. Disconnect Check Harness "B" connector from ECM. Turn ignition on. Connect a jumper wire between ground and terminal No. 75 at Check Harness "B" connector.
  5. With jumper wire connected, Vacuum Switching Valve (VSV) is on. VSV is located near intake manifold at left front of engine. 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 not flow from port "F". If valve operates as specified, go to step 9). If valve does not operate as specified, go to next step.
  6. Remove EGR VSV. Using ohmmeter, measure resistance between valve terminals. Resistance should be 39-45 ohms at 68°F (20°C). Measure resistance between each terminal and body of valve. Resistance should be infinite. If resistance is not as specified, replace VSV. If resistance is as specified, 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 not flow from port "F". Replace VSV as necessary.
  8. If VSV meets all specifications in steps 6) and 7), check circuits between EGR VSV and ECM. See appropriate wiring diagram in WIRING DIAGRAMS - NON-TURBO article. Repair wiring as necessary.
  9. Check EGR vacuum modulator. See SYSTEM/COMPONENT TESTS - NON-TURBO article. Replace as necessary. If EGR vacuum modulator is okay, check EGR valve. See SYSTEM/COMPONENT TESTS - NON-TURBO article. Replace EGR valve 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 EGR temperature sensor.
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