Inventory Upgrade - Transfer Case Control Module Calibration Update

The Transfer Case Control Module (TCCM) Calibration has been revised to improve performance. The new calibration inhibits shifting in or out of 4 High lock at speeds above 45 MPH (72 KPH).

Dealers are to reprogram the TCCM with new calibration.

Perform this service procedure on vehicles in dealer inventory.

Reprogramming the Transfer Case Control Module (TCCM)

Notice: Before reprogramming, please check the battery condition to prevent a reprogram error of the PCM/ECM/TCCM due to battery discharge. Battery voltage must be between 12 and 16 volts during reprogramming. If the vehicle battery is not fully charged, use jumper cables from an additional battery. Be sure to turn off or disable any system that may put a load on the battery such as automatic headlamps, daytime running lights, interior lights, heating, ventilation, and air conditioning (HVAC) system, radio, engine cooling fan, etc. A programming failure or control module damage may occur if battery voltage guidelines are not observed.

The ignition switch must be in the proper position. The Tech 2 prompts you to turn ON the ignition, with the engine OFF. DO NOT change the position of the ignition switch during the programming procedure, unless instructed to do so.

Make certain all tool connections are secure, including the following components and circuits:

DO NOT disturb the tool harnesses while programming. If an interruption occurs during the programming procedure, programming failure or control module damage may occur.

DO NOT turn OFF the ignition if the programming procedure is interrupted or unsuccessful. Ensure that all control module and DLC connections are secure and the TIS terminal operating software is up to date.

Program the transfer case control module using the latest software matching the vehicle. Refer to up-to-date Techline equipment user instructions.

If the transfer case control module fails to program, proceed as follows:

Important: Do not attempt to order the calibration number from GMSPO. The calibration numbers are programmed into the TCCM via a Techline TECH 2 scan tool and the Techline Information System (TIS) 2000 terminal with the calibration update. Use data version 8.0 or later, broadcast to dealers on August 7, 2005; and on TIS CD-ROM version 8.0 / 2005, mailed to dealers beginning August 11, 2005. To complete this service procedure, the TECH 2 must also be updated to release 25.007 or greater. If you cannot access TECH 2 release 25.007 call the Techline Customer Support Center at 1-800-828-6860 (English) or 1-800-503-3222 (French) and it will be provided.

Reprogram TCCM using TECH 2 Remote Programming Method.

1. Use normal "request method" through "Service Programming System" to request information from vehicle.
2. At Techline Terminal enter TIS SIPS programming system.
3. Select Tech 2 from the "Select Diagnostic Tool" window.
4. Select Reprogram ECU from the "Select Programming Process" window.
5. Select Vehicle from the "Select ECU Location" window.
6. Select Next to go to the "Preparing for Communication" instruction screen.
7. Select Next to view the "Validate Vehicle ID Number" screen.
8. Select Next to view "Supported Controllers" screen.
9. Select ATC Active Transfer Case Module from "Supported Controllers" window.
10. Select Next to view the "System Options" window.
11. Select With or Without G94 (Electronic Locking RR Differential) from "System Options" window.
12. Select Next from the "Select Programming Type" window.
13. Select Normal from the "Select Programming Type" window.
14. Select Next to view the "Service Programming System Calibration Selection" screen.
15. Select Next to view "Summary" screen.
16. Verify that the following information is displayed on the "Summary" screen.

•	ID = 1 Current # = 24234136 Selected # = 24237039 Description = New software for improved transfer case operation and rear axle lockup. Also adds enhancements for DTCs B2725, C0359, and B0790.

•	ID = 2 Current # = 12574604 Selected # = 24237037 Description = New software for improved transfer case operation and rear axle lockup. Also adds enhancements for DTCs B2725, C0359, and B0790.

17. Select Next to download the calibration to the TECH 2.
18. Enter "Service Programming Systems".
19. Select Program ECU and follow on screen instructions.
20. Make sure to turn OFF the ignition for 30 seconds after the "Programming is Complete" screen is displayed. Clear diagnostic trouble codes (DTCs), if required.

Do not attempt to order the calibration number from GMSPO. The calibration numbers are programmed into the PCM via a Techline TECH 2 scan tool and the Techline Information System (TIS) 2000 terminal with the calibration update.

Dealers: This upgrade should be performed on all vehicles currently in your inventory as listed in the GM DealerWorld (US) or Dealer Communication Message (Canada) VIN list prior to sale or delivery.