1999 Chevrolet Cutaway 7.4 JFACTORY OEM SERVICE PROCEDURE

Diagnostic Procedures

  1. Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS INTRODUCTION article. After performing OBD system check, go to next step.
  2. Flash ECM with correct software. New ECM must be programmed with theft deterrent module frequency code currently on vehicle. If DTC resets, go to next step. If DTC does not reset, go to step  5.
  3. Verify that equipment being used is functioning properly and that all cable connections are clean and tight. Attempt to flash ECM again. If DTC P0602 resets, go to next step. If DTC P0602 does not reset, go to step  5.
  4. Replace ECM, then go to step  2.
  5. Using scan tool, clear DTCs. Turn ignition off for 15 seconds. Start engine and operate vehicle. Check for DTCs. If DTC P0602 is set, go to step  2. If DTC P0602 is not set, go to next step.
  6. If other DTCs were present during OBD system check and have not been diagnosed, go to applicable DTC. If no other DTCs are present, system is okay.
Factory Service Tools

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.

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