GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2005 🢒 Blazer - 4WD 🢒 Restraints 🢒 SIR 🢒 DTC 004

Circuit Description

At each power up the transfer case shift control module (TCCM) runs a self test on the following:

    • Electronically erasable programmable read-only memory (EEPROM) Checksum
    • Read-only memory (ROM) Checksum
    • Random access memory (RAM) Checksum
    • RAM Malfunction

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC 004 ECU Malfunction

Conditions for Running the DTC
    • Critical operational parameters stored in EEPROM have failed Checksum test indicating invalid data.
    • Masked ROM code has failed Checksum test indicating that masked ROM data is not valid.
    • ROM code has failed Checksum test indicating that ROM data is not valid.
    • One or more ROM locations have failed operational test indicating that some portions of RAM are not functional.

Conditions for Clearing the DTC

The condition for setting the DTC is not present and a momentary loss of battery power at the battery positive voltage circuit.

Test Description

The number below refers to the step number on the diagnostic table.

  1. This step replaces the TCCM.

DTC 004 - RAM/ROM Failure

Step

Action

Yes

No

Schematic Reference: Transfer Case Control Schematics

1

Important: Check the transfer case shift control module for DTCs. The transfer case shift control module is not a class 2 device. DTCs are displayed on the transfer case shift control switch. Use the following 4 steps to obtain DTCs.

  1. Turn OFF the ignition for 10 seconds.
  2. Connect PIN 13 on the data link cable (DLC) to a ground. The DLC is located in the cab under the instrument panel on the driver side.
  3. Turn ON the ignition, with the engine OFF.
  4. Observe the transfer case shift control switch select buttons for flashing codes.

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

2

Replace the TCCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming.

Did you complete the replacement?

Go to Step 3

--

3
  1. Clear all DTCs from memory. Refer to Diagnostic Trouble Code (DTC) Clearing .
  2. Operate the vehicle while pressing each of the buttons on the transfer case shift control switch.

Does the DTC reset?

Go to Step 2

System OK