Product Safety Recall - Transmission Transfer Case-Inspect/Reprogram

This bulletin is being revised to change the transfer case ordering requirements in the "Clean Neutral" test on page 3.

General Motors has decided that a defect which relates to motor vehicle safety exists in certain 2002 Chevrolet TrailBlazer and GMC Envoy model vehicles equipped with four wheel drive. The calibration of the active transfer case module or a range shift collar that was not machined properly may cause insufficient high speed gear engagement. If the gear is not engaged, the vehicle can roll when the transmission is in PARK and a crash could result without warning. A ratcheting noise when the vehicle is in reverse gear or when the driver releases the accelerator pedal while the vehicle is in a drive gear, is a symptom of insufficient gear engagement.

Dealers are to perform a "clean neutral" test, as described in this bulletin, to detect vehicles with range shift collars that were not machined properly. If a ratcheting noise is detected during the test, dealers are to replace the transfer case. Less than 1% of the tested vehicles will require a transfer case replacement. Dealers are to update the active transfer case control module (ATCM) calibration on all vehicles in order to increase gear engagement.

Involved are certain 2002 Chevrolet TrailBlazer and GMC Envoy model vehicles equipped with a transmission transfer case and built within these VIN breakpoints:

Important: Dealers should confirm vehicle eligibility through GMVIS (GM Vehicle Inquiry System) or GM Access Screen (Canada only) or DCS Screen 445 (IPC Only) before beginning recall repairs. [Not all vehicles within the above breakpoints may be involved.]

Involved vehicles have been identified by Vehicle Identification Number. Computer listings containing the complete Vehicle Identification Number, customer name and address data have been prepared, and are being furnished to involved dealers with the recall bulletin. The customer name and address data furnished will enable dealers to follow-up with customers involved in this recall. Any dealer not receiving a computer listing with the recall bulletin has no involved vehicles currently assigned.

These dealer listings may contain customer names and addresses obtained from Motor Vehicle Registration Records. The use of such motor vehicle registration data for any other purpose is a violation of law in several states/provinces/countries. Accordingly, you are urged to limit the use of this listing to the follow-up necessary to complete this recall.

Parts required to complete this recall are to be obtained from General Motors Service Parts Operations (GMSPO). Please refer to your "involved vehicles listing" before ordering parts. Normal orders should be placed on a DRO = Daily Replenishment Order. In an emergency situation, parts should be ordered on a CSO = Customer Special Order.

Important: Due to limited parts availability as well as the cost and size of parts, dealers are encouraged not to order recall parts for use as shelf stock. Parts should only be ordered when the results of the "clean neutral" test determines that it is necessary to replace the transfer case.

Important: It is estimated that less than 1% of involved vehicles will require a transfer case replacement. Most dealers will not replace a single transfer case as part of this recall. Dealers should call the Technical Assistance Center to obtain the transfer case replacement.

(U.S., IPC) The updated calibration for the transfer case control module is included in TIS 2000 version 9.5 or later versions; and on TIS 2000 #10 CD-ROM or later releases. The following table shows the calibration information.

(Canada) Call Technical Assistance Center for instructions on recalibration information. This is mandatory before the vehicle can be released to the customer.

Important: Do not attempt to order the calibration number from GMSPO. The calibration numbers are programmed into the control module via a Techline tool device.

Important: The labor time allowance listed in this recall is different than that currently published in the labor time guide for performing the same operation. In the near future, the labor time guide will be updated with this new information.

Clean Neutral Test

Caution: Please use the parking brake when the vehicle is parked or left unattended.

1. Position the vehicle on a level surface, engine on and apply the service brake.

Important: Ensure that the front and rear of the vehicle are clear of buildings, other vehicles and personnel.

2. Place the transmission in neutral and shift the transfer case to neutral (rotate and hold the transfer case shift selector switch past 4Lo for 15-20 seconds. This must be done in a smooth, non-stop motion. An N indicator light on the switch (in a position past 4Lo) will indicate the shift. This indicator light is difficult to see, especially in low light. The vehicle speed must be below 3 mph (5 km/h)).

2.1.	Shift the transmission to Reverse, then to Neutral and then to Drive; release the service brake, but keep the transfer case in neutral.

Task completed? Yes or No___________

2.2.	While in Drive, VERY LIGHTLY press the throttle, then release the throttle.

2.3.	Shift the transmission to neutral and repeat light throttle, then release the throttle.

2.4.	Shift the transmission to reverse and repeat light throttle.

2.5.

If the vehicle still does NOT move under power (depending on the testing surface, the vehicle could still roll because the transfer case is in neutral) and makes no noise other than a light ticking noise similar to a lifter noise (e.g. ratcheting noise, gear face contact noise) in the transfer case beyond noises that would be expected from the transmission or transfer case as detected at the driver's location (a clean neutral), go to Active Transfer Case Control Module (ATCM) Reprogramming and updated with calibration #12575794.

Answer summary:

Does the vehicle move under power? If Yes_____, replace the transfer case and reprogram the ATCM with updated calibration. If No______, answer the next question.

Does the vehicle make any abnormal noise? If Yes______, replace the transfer case and reprogram the ATCM with udpated calibration. If No_____, do not replace the transfer case, but reprogram the ATCM with updated calibration.

Keep a copy of this worksheet in the vehicle history file.

Order the transfer case directly from GMSPO as it is no longer required to call TAC to order the transfer case.

Removal Procedure

1. Raise the vehicle.
2. Remove the fuel tank shield retaining bolts.
3. Remove the fuel tank shield.
4. Remove the rear propeller shaft.

4.1.	Reference mark the propeller shaft to the rear axle pinion yoke.

4.2.	Remove the bolts and the yoke retainers from the rear axle pinion yoke.

4.3.	Disconnect the propeller shaft from the rear axle pinion yoke.

4.4.	Slide the propeller shaft rearward in order to disconnect the propeller shaft from the transfer case.

5. Drain the transfer case.

5.1.	Remove the drain plug and drain the fluid into a suitable container.

5.2.	Install the drain plug.

Tighten
Tighten the drain plug to 34 N·m (25 lb ft).

6. Remove the front propeller shaft.

6.1.	Reference mark the propeller shaft to the front axle pinion yoke.

6.2.	Remove the bolts and the yoke retainers from the front axle pinion yoke.

6.3.	Disconnect the propeller shaft from the front axle pinion yoke.

6.4.	Remove the propeller shaft from the transfer case.

7. Remove the fuel lines from the retainer.
8. Remove the electrical harness from the retainers.
9. Remove the electrical connector from the speed sensors.
10. Remove the motor/encoder electrical connector.
11. Remove the transfer case wiring harness.
12. Remove the vent hose.
13. Install a transmission jack for the transfer case.
14. Remove the transfer case mounting nuts.
15. Remove the transfer case from the vehicle.
16. Remove the transfer case gasket.

Installation Procedure

Notice: To avoid part damage, verify that transfer case fluid is present. If required, add or fill transfer case fluid. Refer to SI for fluid specifications and fill instructions.

Important: DO NOT use silicone sealant in place or with the transfer case gasket.

1. Replace the transfer case gasket.
2. Install the transfer case in the vehicle.
3. Install the transfer case mounting nuts.

Tighten
Tighten the nuts to 47 N·m (35 lb ft).

4. Remove the transmission jack stand.
5. Install the transfer case speed sensors electrical connectors.
6. Install the vent hose.
7. Install the motor/encoder electrical connector.
8. Install the transfer case harness to the transfer case.
9. Install the transfer case wiring harness to the retainers.
10. Install the fuel lines to the retainer.
11. Install the rear propeller shaft.

11.1.

Install the propeller shaft into the transfer case.

11.2.

Install the propeller shaft to the rear axle pinion yoke. Align the reference marks made during removal.

11.3.

Install the yoke retainers and the bolts.

Tighten
Tighten the bolts to 20 N·m (15 lb ft).

12. Install the front propeller shaft.

12.1.

Install the propeller shaft to the transfer case.

12.2.

Install the propeller shaft to the front axle pinion yoke. Align the reference marks made during removal.

12.3.

Install the yoke retainers and the bolts.

Tighten
Tighten the bolts to 20 N·m (15 lb ft).

13. Install the fuel tank shield.
14. Install the fuel tank shield retaining bolts.

Tighten
Tighten the bolts to 25 N·m (18 lb ft).

15. Lower the vehicle and continue with Active Transfer Case Control Module reprogramming.

Active Transfer Case Control Module Reprogramming

1. Reprogram the transfer case control module with calibration P/N 12575794.

1.1.	Connect the scan tool to the vehicle.

1.2.	Power up the scan tool and select the Service Programming feature.

1.3.	Select the appropriate vehicle.

1.4.	Press the Request Info button on the scan tool.

1.5.	Connect the scan tool to the computer station.

1.6.	Follow the menu select items for reprogramming and provide information as to what device you are programming and whether you are reprogramming or replacing the electronic control unit (ECU).

1.7.	Select "vehicle" from the selection menu.

1.8.	Select "ATC Active Transfer Case Module" to program.

1.9.	Select "Normal" for Programming Type.

1.10.

Select the applicable software calibrations.

1.11.

Transfer data file to the scan tool.

1.12.

Position the left side second row seat in order to access the rear fuse block.

1.13.

Remove the No. 6 (Liftgate Module/Driver Seat Module) fuse.

1.14.

Reconnect the scan tool to the vehicle.

1.15.

Turn ON the ignition, with the engine OFF.

1.16.

Select the Service Programming feature on the scan tool.

1.17.

Press the Program button on the scan tool.

1.18.

Install fuse and reposition the seat.

2. Perform the system check by shifting transfer case to all modes of operation.
3. Install the GM Recall Identification Label.

FOR US AND IPC

Place a Recall Identification Label on each vehicle corrected in accordance with the instructions outlined in this Product Recall Bulletin. Each label provides a space to include the recall number and the five (5) digit dealer code of the dealer performing the recall service. This information may be inserted with a typewriter or a ball point pen.

Put the Recall Identification Label on a clean and dry surface of the radiator core support in an area that will be visible to people servicing the vehicle. When installing the Recall Identification Label, be sure to pull the tab to allow the adhesion of the clear protective covering. Additional Recall Identification Labels for US dealers can be obtained from Dealer Support Materials by calling 1-866-700-0001 (Monday-Friday, 8:00 am to 5:00 pm EST). Ask for Item Number S-1015 when ordering.

Additional Recall Identification Labels for IPC dealers can be obtained from your Regional Marketing Office.

FOR CANADA

Place a Recall Identification Label on each vehicle corrected in accordance with the instructions outlined in this Product Recall Bulletin. Each label provides a space to include the recall number and the five (5) digit dealer code of the dealer performing the recall service. This information may be inserted with a typewriter or a ball point pen.

Put the Recall Identification Label on a clean and dry surface of the radiator core support in an area that will be visible to people servicing the vehicle. Additional Recall Identification Labels for Canadian dealers can be obtained from DGN by calling 1-800-668-5539 (Monday-Friday, 8:00 am to 5:00 pm EST). Ask for Item Number GMP 91 when ordering.

Submit a Product Recall Claim with the information indicated below:

Refer to the General Motors WINS Claims Processing Manual for details on Product Recall Claim Submission.

FOR US AND CANADA

Customers will be notified of this recall on their vehicles by General Motors (see copy of customer letter included with this bulletin).

FOR IPC

Letters will be sent to known owners of record located within areas covered by the US National Traffic and Motor Vehicle Safety Act. For owners outside these areas, dealers should notify customers using the attached suggested dealer letter.

FOR US AND IPC (US States, Territories, and Possessions)

The US National Traffic and Motor Vehicle Safety Act provides that each vehicle which is subject to a recall of this type must be adequately repaired within a reasonable time after the customer has tendered it for repair. A failure to repair within sixty days after tender of a vehicle is prima facie evidence of failure to repair within a reasonable time. If the condition is not adequately repaired within a reasonable time, the customer may be entitled to an identical or reasonably equivalent vehicle at no charge or to a refund of the purchase price less a reasonable allowance for depreciation. To avoid having to provide these burdensome remedies, every effort must be made to promptly schedule an appointment with each customer and to repair their vehicle as soon as possible. In the recall notification letters, customers are told how to contact the US National Highway Traffic Safety Administration if the recall is not completed within a reasonable time.

FOR ALL

All unsold new vehicles in dealers' possession and subject to this recall MUST be held and inspected/repaired per the service procedure of this recall bulletin BEFORE customers take possession of these vehicles.

Dealers are to service all vehicles subject to this recall at no charge to customers, regardless of mileage, age of vehicle, or ownership, from this time forward.

Customers who have recently purchased vehicles sold from your vehicle inventory, and for which there is no customer information indicated on the dealer listing, are to be contacted by the dealer. Arrangements are to be made to make the required correction according to the instructions contained in this bulletin. This could be done by mailing to such customers a copy of the customer letter accompanying this bulletin. Recall follow-up cards should not be used for this purpose, since the customer may not as yet have received the notification letter.

In summary, whenever a vehicle subject to this recall enters your vehicle inventory, or is in your dealership for service in the future, please take the steps necessary to be sure the recall correction has been made before selling or releasing the vehicle.

Dear General Motors Customer:

This notice is sent to you in accordance with the requirements of the National Traffic and Motor Vehicle Safety Act.

General Motors has decided that a defect which relates to motor vehicle safety exists in certain 2002 Chevrolet TrailBlazer and GMC Envoy model vehicles equipped with four wheel drive. The calibration of the automatic transfer case module or a range shift collar that was not machined properly may cause insufficient high speed gear engagement. If the gear is not engaged, the vehicle can roll when the transmission is in PARK and a crash could result without warning. A ratcheting noise when the vehicle is in reverse gear or when the driver releases the accelerator pedal while the vehicle is in a drive gear, is a symptom of insufficient gear engagement.

Your dealer will perform a system test, and, if necessary, replace the transfer case. On all vehicles, your dealer will update the transfer case control module calibration to increase high speed gear engagement. This service will be performed for you at no charge. Until that service is completed, the driver should always apply the parking brake before exiting the vehicle.

The length of time required to perform this service for most vehicles is half an hour. If the transfer case is replaced, the time is two and one half hours. Additional time may be required to schedule and process your vehicle. If you dealer has a large number of vehicles awaiting service, this additional time may be significant. Please ask your dealer if you wish to know how much additional time will be needed to schedule, process and repair your vehicle.

Please contact your <Division> dealer as soon as possible to arrange a service date. Parts are available and instructions for making this correction have been sent to your dealer.

Your <Division> dealer is best equipped to obtain parts and provide services to correct your vehicle as promptly as possible. Should your dealer be unable to schedule a service date within a reasonable time, you should contact the appropriate Customer Assistance Center at the number listed below:

If, after contacting the appropriate customer assistance center, you are still not satisfied that we have done our best to remedy this condition without charge and within a reasonable time, you may wish to write the Administrator, National Highway Traffic Safety Administration, 400 Seventh Street SW, Washington, DC 20590 or call 1-888-327-4236.

The attached customer reply card identifies your vehicle. Presentation of this card to your dealer will assist in making the necessary correction in the shortest possible time. If you no longer own this vehicle, please let us know by completing the attached and mailing it in the postage paid envelope.

Your dealer will provide you with courtesy transportation if your vehicle requires a transfer case replacement and needs to be held for more than a day for this repair. Please refer to your Owner's Manual and your dealer for details on Courtesy Transportation.

We are sorry to cause you this inconvenience; however, we have taken this action in the interest of your safety and continued satisfaction with our products.

General Motors Corporation

Enclosure