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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 P0404 - EGR System Performance >> 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 control pressure/BARO sensor. Start and warm engine to normal operating pressure. Operate engine at idle. Observe vacuum gauge. If vacuum is 5-7 in. Hg, go to next step. If vacuum is not 5-7 in. Hg, go to step 4).
  3. Repair restriction between EGR control pressure/BARO sensor and vacuum "T" fitting. After repairs, go to step 5).
  4. Replace EGR control pressure/BARO sensor. After replacing sensor, go to next step.
  5. After repairs, reset EGR Adaptive Learn Matrix (ALM) cells using scan tool. After resetting EGR ALM cells, go to next step.
  6. Using scan tool, select DTC, CLEAR INFO. Start and warm engine to normal operating temperature. 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).
  7. Using scan tool, select CAPTURE INFO, REVIEW INFO. If any undiagnosed DTC(s) are displayed, go to applicable DTC test.
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