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Home >> Geo >> 1996 >> Metro Base, 2D Hatchback, 1.3 9 >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes >> Circuit Tests >> DTC P0400 - EGR System >> Diagnosis & Repair

Diagnosis & Repair

  1. Start engine and allow to reach normal operating temperature. If engine runs rough, or idle is unstable, go to step 5). If engine runs okay, go to next step.
  2. Connect scan tool to DLC. Start engine. Select EGR by-pass valve ON. If idle speed drops and engine runs rough, go to next step. If no change in idle quality is observed, go to step 7).
  3. Ensure vehicle is in Park (A/T) or Neutral (M/T) with parking brake applied. Observe EGR valve diaphragm while accelerating engine. If EGR valve opens slightly, go to next step. If EGR valve does not open, go to step 14).
  4. Select CLEAR INFORMATION function on scan tool. Operate vehicle within FREEZE FRAME conditions. If DTC P0400 resets, repeat step 1). If DTC P0400 does not reset, check for an intermittent problem. See TESTS W/O CODES article.
  5. Disconnect vacuum hose from EGR valve. If engine idle stabilizes, go to next step. If engine idle does not change, go to step 8).
  6. Connect a vacuum gauge to EGR vacuum supply hose and note reading. Disconnect EGR by-pass valve harness connector. If vacuum gauge drops to zero in. Hg, go to step 21). If vacuum reading does not change, replace EGR by-pass valve. Retest system.
  7. Using a glove or rag, lift up on EGR valve diaphragm. If engine idle speed drops or engine runs rough, go to step 9). If no change in idle quality is observed, go to next step.
  8. Remove EGR valve and inspect for sticking pintle, clogged passages, or a ruptured diaphragm. Repair as necessary. If no problems are found, replace EGR valve. Retest system.
  9. Connect a vacuum gauge to EGR vacuum supply hose. Using scan tool, turn EGR by-pass valve ON. If vacuum gauge reads 15-21 in. Hg, replace EGR valve. Retest system. If vacuum gauge reading is not as specified, go to next step.
  10. Check for manifold vacuum to EGR by-pass valve. If vacuum is present, go to next step. If no vacuum is present, repair as necessary. Retest system.
  11. Turn ignition off. Disconnect EGR by-pass valve harness connector. Using an ohmmeter, measure resistance between EGR by-pass valve terminals. If resistance is 33-40 ohms at 68°F (20°C), go to next step. If resistance is not as specified, replace EGR by-pass valve. Retest system.
  12. Turn ignition on. Using a test light connected to ground, probe ignition feed circuit (White/Blue wire) to EGR by-pass valve. If test light comes on, go to next step. If test light does not come on, check for blown FI fuse (15-amp) in passenger compartment fuse box, or open White/Blue wire. Repair as necessary. Retest system.
  13. Check for open Red/Black wire between EGR by-pass valve and PCM connector C1, terminal No. 5. Repair as necessary. If wire is okay, replace PCM. Retest system.
  14. Connect a vacuum gauge to pressure transducer side of EGR solenoid vacuum valve. With engine running at normal operating temperature, raise idle speed to 3000 RPM. Using scan tool, turn EGR solenoid vacuum valve ON. If vacuum gauge reading is 5 in. Hg or more, go to next step. If reading is not as specified, go to step 17).
  15. Remove EGR pressure transducer. Place a finger over port "Q", and blow into port "P". If air passes through filter part of pressure transducer, go to next step. If air does not pass through filter, replace EGR pressure transducer. Retest system.
  16. Connect a vacuum pump to EGR pressure transducer port "P", and plug port "Q". Apply vacuum to port "P" while blowing into port "A". If vacuum pump will only maintain vacuum while blowing into port "A", see TESTS W/O CODES article. If vacuum does not hold or release as specified, replace EGR pressure transducer. Retest system.
  17. Check for ported vacuum to EGR solenoid vacuum valve. Repair as necessary. If vacuum supply is okay, go to next step.
  18. Turn ignition off. Disconnect EGR solenoid vacuum valve harness connector. Using an ohmmeter, measure resistance between EGR solenoid vacuum valve terminals. If resistance is 33-40 ohms at 68°F (20°C), go to next step. If resistance is not as specified, replace EGR solenoid vacuum valve. Retest system.
  19. Turn ignition on. Using a test light connected to ground, probe ignition feed circuit to EGR solenoid vacuum valve (White/Blue wire). If test light comes on, go to next step. If test light does not come on, check for blown FI fuse (15-amp), or open White/Blue wire. Repair as necessary. Retest system.
  20. Check for open or short in Green wire between EGR solenoid vacuum valve and PCM connector C1, terminal No. 6. Repair as necessary. If wire is okay, replace PCM. Retest system.
  21. Check for short in Red/Black wire between EGR by-pass valve and PCM connector C1, terminal No. 5. Repair as necessary. If wire is okay, replace PCM. Retest system.
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