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Home › Chevrolet › 2000 › Tracker 4D Utility, 4WD, Automatic › Repair and Diagnosis › Engine Performance › System › Engine Control System Self-Diagnostics › Diagnostic Tests › DTC P0400: Exhaust Gas RECIRCULATION Flow Malfunction › Diagnostic Procedures

Diagnostic Procedures

  1. Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC SYSTEM CHECK  under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
  2. Check for DTCs. If DTC P0403 also set, diagnose affected DTC. If DTC P0403 is not set, go to next step.
  3. Start and operate engine to normal operating temperatures. If engine runs rough or if idle is unstable, go to step  12. If engine does not run rough or if idle is not unstable, go to next step.
  4. Using scan tool, clear DTCs. Start engine. Using scan tool, gradually command EGR valve to open 100 percent. If engine runs rough or stalls, go to step  10. If engine does not run rough or does not stall, go to next step.
  5. Start engine. Using a test light connected to ground, backprobe EGR control terminals No. 1 (EGR coil control) and No. 4 (EGR coil control). If test light illuminates on both circuits, continue to backprobe both EGR control circuits while commanding EGR valve to open at 5 percent using scan tool. Test light should illuminate and then turn off when EGR valve is commanded open. If test light operates as commanded, go to next step. If test light does not operate as commanded, go to step  7.
  6. Start engine. Using test light connected to ground, backprobe EGR control terminals No. 3 (EGR coil control) and No. 6 (EGR coil control). Test light should not illuminate on both circuits. Continue to backprobe both EGR control circuits while commanding the EGR valve open at 5 percent using scan tool. Test light should illuminate when EGR valve is commanded open. If test light operates as commanded, go to step  8. If test light does not operate as commanded, go to next step.
  7. Turn ignition off. Disconnect EGR valve harness connector. Using a DVOM, check resistance between EGR valve coil windings (between terminals No. 1 and 2; terminals 2 and 3; terminals 5 and 6; terminals 4 and 5). Resistance should be 20-24 ohms at 68°F (20°C). Check resistance between EGR valve body and EGR valve terminals No. 2 and No. 5. Resistance should be infinite. If resistance readings are as specified, go to step  9. If resistance readings are not as specified, go to step  17.
  8. Remove EGR valve. Check all EGR passages for any obstruction or blockage. Check EGR valve for physical damage or carbon deposits. Repair or replace as necessary. After repairs, go to step  19. If no problems were found, go to step  17.
  9. Disconnect EGR valve harness connector. Turn ignition on, with engine off. Connect a test light between ground and EGR valve harness connector terminal No. 2, then to terminal No. 5. If test light illuminated on both circuits, go to step  16. If test light did not illuminate on both circuits, go to step  15.
  10. Check vehicle for any condition that can affect accuracy of MAP sensor, such as a malfunctioning or incorrectly calibrated MAP sensor, faulty manifold vacuum supply to sensor or an engine performance concern that can affect engine manifold vacuum readings. Repair as necessary. After repairs, go to step  19. If no problems were found, go to next step.
  11. Fault is not present. Check for any stored and undiagnosed DTC(s) and diagnose as necessary.
  12. With engine running, disconnect EGR valve harness connector. If engine performance improves when connector is disconnected, go to step  14. If engine performance does not improve when connector is disconnected, go to next step.
  13. Remove EGR valve. Check EGR valve for sticking open or leaking EGR valve and gasket Repair or replace as necessary. After repairs, go to step  19.
  14. Check EGR coil control circuits for short to ground. Repair as necessary. After repairs, go to step  19. If circuits are okay, go to step  18.
  15. Repair ignition positive voltage supply to EGR valve. After repairs, go to step  19.
  16. Check for open or short in EGR coil control circuits between EGR valve and PCM. Repair as necessary. After repairs, go to step  19. If circuits are okay, go to step  18.
  17. Replace EGR valve. After replacing EGR valve, go to step  19.
  18. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to next step.
  19. Using scan tool, clear DTCs. Operate vehicle within FREEZE FRAME conditions that set the DTC or until DTC P0400 diagnostic test has run. Review scan tool data and check for DTCs. If other DTC(s) are set, diagnose affected DTC(s). If no other DTC(s) are set, system is okay.
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