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Home >> Chevrolet >> 1997 >> C3500 HD 7.4 J, Automatic >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 3 (Engine Controls - Tests W/Codes - 6.5L) >> Diagnostic Trouble Codes >> DTC P0400 - EGR Flow Malfunction >> Diagnostic Procedures

Diagnostic Procedures

WARNING: This page is about a different variant/trim than selected.
  1. Perform Powertrain ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the BASIC TESTING - 6.5L DIESEL article. Then go to next step.
  2. Install vacuum gauge in place of EGR valve. Start engine and operate at idle. Apply parking brakes and block drive wheels. Place transmission in Drive. Observe vacuum gauge. If vacuum reading is 5-7 in. Hg, go to next step. If vacuum is not 5-7 in. Hg, to step 5).
  3. Turn ignition off. Install a hand-held vacuum pump to EGR valve. Start and operate engine at idle, with transmission in Park. Using scan tool, observe cylinder air display while applying 15 in. Hg to EGR valve. If scan tool display reads a decrease of .10 g/cyl. or greater, go to next step. If reading does not indicate a decrease of .10 g/cyl. or greater, go to step 7).
  4. DTC is intermittent. If no additional DTCs are set, see DIAGNOSTIC AIDS. If any additional DTCs are set, go to applicable DTC test.
  5. Check vacuum source at solenoid assembly. If vacuum is 15 in. Hg, go to next step. If vacuum is not 15 in. Hg, go to step 8).
  6. Check for restricted or leaky vacuum hose from solenoid to EGR valve. Repair as necessary. After repairs, go to step 9).
  7. Replace EGR valve. After replacing EGR valve, go to step 9).
  8. Repair vacuum pump. After repairs, go to next step.
  9. After repairs, reset EGR Adaptive Learn Matrix (ALM) cells using scan tool. After resetting EGR ALM cells, go to next step.
  10. Using scan tool, select CLEAR INFO. Start and warm engine to normal operating temperature. Test drive vehicle. Select DTC, SPECIFIC, then enter DTC P0404. Operate vehicle within the conditions for setting this DTC. If scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, repeat step 2).
  11. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.
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