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Home >> Chevrolet >> 2001 >> Impala LS >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System Self-Diagnostics - 3.8L >> Diagnostic Tests >> DTC P0404: EGR Open Position Performance >> Diagnostic Procedures
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Diagnostic Procedures

NOTE: For EGR connector wire colors and circuit identification, see EGR CONNECTOR TERMINAL & CIRCUIT IDENTIFICATION  table under DTC P0403: EGR SOLENOID CONTROL CIRCUIT.
  1. Perform powertrain diagnostic system check. See POWERTRAIN DIAGNOSTIC SYSTEM CHECK  under SELF-DIAGNOSTIC SYSTEM. After performing powertrain diagnostic system check, go to next step.
  2. Turn ignition on. Using scan tool, check if DTC P0403 or P0405 is present. If either of these DTCs are present, diagnose these DTCs first. If DTC P0403 or P0405 is not present, using scan tool, command EGR valve from zero to 100 percent. If desired and actual EGR position remain within 15 percent of each other at all commanded positions, go to next step. If desired and actual EGR position do not remain within 15 percent of each other, go to step  4.
  3. Observe FREEZE FRAME/FAILURE RECORDS data for this DTC. Turn ignition off for 30 seconds. Start engine. Operate vehicle within code enable criteria or as close to FREEZE FRAME/FAILURE RECORDS data as possible. If this DTC failed this ignition cycle, go to next step. If this DTC did not fail this ignition cycle, see DIAGNOSTIC AIDS .
  4. Turn ignition off. Disconnect EGR. See Figure or Figure . Turn ignition on, engine off. Using scan tool, observe EGR position sensor parameter. If scan tool indicates EGR position sensor is zero percent, go to next step. If scan tool does not indicate EGR position sensor is zero percent, go to step  8.
  5. Measure voltage between EGR connector terminals "B" and "D". See Figure. If voltage is about 5 volts, go to next step. If voltage is not about 5 volts, go to step  7.
    6. NOTE: If fuse blows, locate and repair a short to ground in signal circuit.
  6. Connect a fused jumper between EGR connector terminals "C" and "D". If scan tool indicates EGR position sensor is about 100 percent, go to step  12. If scan tool does not indicate EGR position sensor is about 100 percent, go to step  10.
  7. Measure voltage between EGR connector terminal "D" and ground. If voltage is about 5 volts, go to step  9. If voltage is not about 5 volts, go to step  11.
  8. Check EGR position signal circuit for short to voltage. If problem was found, repair as necessary. After repairs, go to step  16. If problem was not found, go to step  13.
  9. Check EGR position sensor ground circuit for open or high resistance. If problem was found, repair as necessary. After repairs, go to step  16. If problem was not found, go to step  13.
  10. Check EGR signal circuit for high resistance or high resistance short to ground. If problem was found, repair as necessary. After repairs, go to step  16. If problem was not found, go to step  14.
  11. Check EGR 5-volt reference circuit for open, short to ground, or short to voltage. If problem was found, repair as necessary. After repairs, go to step  16. If problem was not found, go to step  14.
  12. Inspect for poor connections at the harness connector of the EGR valve. If problem was found, repair as necessary. After repairs, go to step  16. If problem was not found, go to step  14.
  13. Check PCM connectors for poor connections. If problem was found, repair as necessary. After repairs, go to step  16. If problem was not found, go to step  15.
  14. Replace EGR valve. After repairs, go to step  16.
  15. Replace PCM. Program replacement PCM. See POWERTRAIN CONTROL MODULE  under PROGRAMMING. After repairs, go to next step.
  16. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Start engine. Operate vehicle within code enable criteria. If DTC runs and passes, go to next step. If DTC does not run and pass, go to step  2.
  17. Using scan tool, observe stored information. If scan tool displays any DTCs that have not been diagnosed, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If scan tool does not display any DTCs, system is okay.
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