2004 Chevrolet ClassicFACTORY OEM SERVICE PROCEDURE

Removal Procedure

Service should normally consist of either replacement of the PCM or electronically erasable programmable read only memory (EEPROM) re-programming.

If the diagnostic procedures call for the PCM to be replaced, the PCM should be inspected first in order to verify the PCM is the correct part. DTC P0602 indicates the EEPROM programming has malfunctioned. When DTC P0602 is set, re-program the EEPROM.

IMPORTANT: It is necessary to record the remaining engine oil life. If the replacement module is not programed with the remaining engine oil life, the engine oil life will default to 100%. If the replacement module is not programmed with the remaining engine oil life, the engine oil will need to be changed at 5000 km (3,000 mi) from the last engine oil change.
  1. Using a scan tool, retrieve the percentage of remaining engine oil. Record the remaining engine oil life.
  2. Disconnect the negative battery cable. Refer to Battery Negative Cable Disconnect/Connect Procedure in Engine Electrical.
  3. Remove the left closeout/insulator panel. Refer to Closeout/Insulator Panel Replacement - Left in Instrument Panel, Gages, and Console.
  4. Fig 1: Identifying PCM Harness Connectors
    GM791323Courtesy of GENERAL MOTORS CORP.
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:

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

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