LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Chevrolet >> 2002 >> 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
April 5, 2026: LEMON Manuals is launched! Read the announcement.

Diagnostic Procedures

  1. Perform Diagnostic System Check - Engine Controls. See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS  under SELF-DIAGNOSTIC SYSTEM. After performing Diagnostic System Check - Engine Controls, go to next step.
    2. NOTE: Using scan tool, check if DTC P0403 or P0405 is present. If either of these DTCs are present, diagnose these DTCs first. See DTC P0403: EGR SOLENOID CONTROL CIRCUIT  or DTC P0405: EGR POSITION SENSOR CIRCUIT - LOW VOLTAGE  .
  2. Turn ignition on. If DTC P0403 or P0405 is not present, using scan tool, command EGR valve from zero to 100 percent. Does the EGR position sensor remain within 15 percent of the desired EGR position at all commanded positions? If yes, go to next step. If no, 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 Conditions for Running DTC or as close to FREEZE FRAME/FAILURE RECORDS data as possible. Does the DTC fail this ignition cycle? If yes, go to next step. If no, see DIAGNOSTIC AIDS .
  4. Turn ignition off. Disconnect EGR. Turn ignition on, engine off. Using scan tool, observe EGR position sensor parameter. Does the scan tool indicate that the EGR position sensor is zero percent? If yes, go to next step. If no, go to step  8.
  5. Measure the voltage from the 5-volt reference circuit of the EGR position sensor to the ground circuit of the EGR position sensor. Does the DMM display voltage near 5 volts? If yes, go to next step. If no, 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 the 5-volt reference circuit of the EGR position sensor and the EGR pintle position signal circuit of the EGR position sensor. Does the scan tool indicate that the EGR position sensor is near 100 percent? If yes, go to step  12. If no, go to step  10.
  7. Measure the voltage from the 5-volt reference circuit of the EGR position sensor to a good ground. Does the DMM display voltage near 5 volts? If yes, go to step  9. If no, go to step  11.
  8. Test the EGR pintle position signal circuit for a short to voltage. Did you find and correct the condition? If yes, go to step  16. If no, go to step  13.
  9. Check EGR position sensor ground circuit for open or high resistance. Did you find and correct the condition? If yes, go to step  16. If no, go to step  13.
  10. Check EGR signal circuit for high resistance or high resistance short to ground. Did you find and correct the condition? If yes, go to step  16. If no, go to step  14.
  11. Check EGR 5-volt reference circuit for open, short to ground, or short to voltage. Did you find and correct the condition? If yes, go to step  16. If no, go to step  14.
  12. Inspect for poor connections at the harness connector of the EGR valve. Did you find and correct the condition? If yes, go to step  16. If no, go to step  14.
  13. Check PCM connectors for poor connections. Did you find and correct the condition? If yes, go to step  16. If no, 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 Conditions for Running DTC. Does DTC run and pass? If yes, go to next step. If no, go to step  2.
  17. Using scan tool, observe stored information. Does scan tool displays any DTCs that have not been diagnosed? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, system is okay.
scientia non olet · About LEMON Manuals