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Home >> GMC >> 1998 >> Forward Control 7.4 B >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes - 7.4L >> Diagnostic Trouble Codes >> DTC P0602 - VCM Not Programmed >> Diagnostic Procedures
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Diagnostic Procedures

  1. Perform POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK , then go to next step.
  2. Flash VCM with current software. If DTC is reset, go to next step. If DTC does not reset, go to step 5).
  3. Verify that test equipment used is operating properly and that all connections are clean and tight. Attempt to flash VCM again. If DTC resets, go to next step. If DTC does not reset, go to step 5).
  4. Replace VCM. Program replacement VCM using required equipment. After repair is completed, go to next step.
  5. Using scan tool, select DTC, CLEAR INFO function. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, then enter this DTC. Operate vehicle within 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).
  6. Using scan tool, select CAPTURE INFO, REVIEW INFO function. If any undiagnosed DTCs are displayed, go to applicable DTC test.
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