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Home >> Buick >> 1996 >> Roadmaster Base >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control Systems - Tests W/Codes >> Diagnostic Trouble Codes >> DTC P0403 - EGR Solenoid Control Circuit >> Diagnostic Procedures

Diagnostic Procedures

  1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
  2. Turn ignition on, with engine off. Using scan tool, command EGR solenoid on and off. If solenoid turns on and off as commanded, go to next step. If solenoid does not respond as commanded, go to step 5).
  3. Turn ignition off. Disconnect PCM harness connector containing solenoid control circuit. Turn ignition on. Using DVOM, set DVOM to 10-amp scale. Check current from solenoid control circuit in PCM harness connector to ground for 2 minutes. If current draw is less than .75 amp, but not zero amps. If current draw is not as specified, go to next step. If current draw is as specified, see DIAGNOSTIC AIDS.
  4. Turn ignition off. Disconnect EGR solenoid. Using DVOM, check resistance from solenoid control circuit in PCM harness connector and ground. If resistance is infinite, go to step 12). If resistance is not as specified, go to step 10).
  5. Turn ignition off. Disconnect EGR solenoid. Connect test light between solenoid harness connectors. Turn ignition on. Using scan tool, command solenoid on and off. If test light turns on and off with each command, go to step 8). If test light does not turn on and off with each command, go to next step.
  6. Connect test light to ground and probe the ignition feed circuit in the solenoid harness connector. If test light illuminates, go to next step. If test light does not illuminate, go to step 11).
  7. Turn ignition off. Reconnect EGR solenoid. Disconnect PCM connector containing the solenoid control circuit. Turn ignition on. Using a fused jumper wire, jumper solenoid control circuit to ground in PCM harness connector. If solenoid operates, go to step 9). If solenoid does not operate, go to step 10).
  8. Check connections at EGR solenoid. Repair as necessary. After repairs, go to step 14). If connections are okay, go to step 12).
  9. Check connections at PCM. Repair as necessary. After repairs, go to step 14). If connections are okay, go to step 13).
  10. Repair faulty EGR solenoid control circuit. After repairs, go to step 14).
  11. Repair faulty EGR solenoid ignition feed circuit. After repairs, go to step 14).
  12. Replace EGR solenoid. After replacing EGR solenoid, go to step 14).
  13. Replace PCM. Program replacement PCM using required equipment. After repair is completed, go to step 14).
  14. Using scan tool, select DTC, CLEAR INFO function. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, then enter DTC P0402. Operate vehicle within conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool did not indicate that this test ran and passed, repeat step 2).
  15. Using scan tool, select CAPTURE INFO, REVIEW INFO function. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.
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