Incorrect Vehicle Speed Sensor Calibration

General Motors has decided that certain 1998 Chevrolet and GMC M vans may have been built using the incorrect vehicle speed sensor calibration file. Vehicles with a 3.23 gear ratio axle will indicate a vehicle speed 5.47% slower than the actual vehicle speed and the odometer will accumulate 5.47% less miles than the vehicle actually traveled. Vehicles with a 3.42 gear ratio axle will indicate a vehicle speed 5.85% faster than the actual vehicle speed and the odometer will accumulate 5.85% more miles than the vehicle actually traveled.

To correct this condition, dealers are to reprogram the vehicle control module and adjust the odometer to reflect the correct mileage.

Involved are certain 1998 Chevrolet and GMC M vans equipped with 3.23 rear axle ratio (RPO GU5) or 3.42 rear axle ratio (RPO GU6) and built within the following VIN breakpoints:

Important: Dealers should confirm vehicle eligibility through VISS (Vehicle Information Service System) prior to beginning campaign 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 campaign bulletin. The customer name and address data furnished will enable dealers to follow-up with customers involved in this campaign. Any dealer not receiving a computer listing with the campaign bulletin has no involved vehicles currently assigned.

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

No parts are required for this campaign.

Customers will be notified of this campaign on their vehicles by General Motors (see copy of typical customer letter included with this bulletin - actual divisional letter may vary slightly).

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

Dealers are to service all vehicles subject to this campaign 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. Campaign 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 campaign enters your vehicle inventory, or is in your dealership for service in the future, please take the steps necessary to be sure the campaign correction has been made before selling or releasing the vehicle.

REMOVAL OF INSTRUMENT CLUSTER

1. Record the mileage shown on the odometer.
2. Disconnect the negative battery cable.
3. Set the parking brake, turn the ignition key to the ON position and move the gear selector to the 1st gear position.
4. Lower the tilt column to the lowest position (if equipped).
5. Gently pull the instrument panel trim plate away from the instrument panel until all fasteners are released.
6. Disconnect the electrical connectors as necessary, and remove the trim plate.
7. Remove the four screws retaining the instrument cluster to the instrument panel.
8. Gently pull the instrument cluster straight out and remove from the vehicle.
9. Calculate the actual mileage for the vehicle using the appropriate formula below:

•	FOR VEHICLES WITH A 3.23 AXLE (GU5):

•	mileage X 0.0547 = amount to be ADDED to the mileage reading taken in Step 1.

•	FOR VEHICLES WITH A 3.42 AXLE (GU6):

•	mileage X 0.0585 = amount to be DEDUCTED from the mileage reading taken in Step 1.

10. Arrange for pick-up or delivery of the cluster with your ACDelco Service Center. For a listing of service centers, refer to your divisional bulletin.
11. Type the required information in the red shaded area of the ACDelco 1078 form, taking care to type the correct VIN.
12. Provide the cluster and ACDelco 1078 form to the ACDelco Service Center. Retain Dealer copy, attach to R.O.

INSTALLATION OF INSTRUMENT CLUSTER

1. When you receive the instrument cluster back from ACDelco, set the instrument cluster into the instrument panel and align the cluster to the instrument panel connector and gently press the cluster into place to seat the connector.
2. Install the four retaining screws for the cluster.
3. Place the instrument panel trim plate into the opening and connect any necessary connectors.
4. Gently press the trim plate into place until the retainers are fully engaged.
5. Move the gear selector into PARK, and turn the ignition to the OFF position and release the park brake.
6. Connect the negative battery cable.

VCM PROGRAMMING

The new calibration is available on CD #15 for 1998 and later versions from STG. The calibration is programmed into the vehicle's VCM via a Techline Tool. Use a Techline Terminal or scan tool to perform the learn procedure and program the VCM.

1. To ensure VCM programming/RPO configuration, confirm that the following conditions exist in order to prepare for VCM programming:

•	The battery is fully charged.

•	The ignition switch is in the RUN position.

•	The Data Link Connector (DLC) is accessible.

2. Refer to the latest Techline Terminal and equipment user's instructions.
3. Clear the diagnostic trouble codes (DTCs) after the programming is complete.
4. Install the GM Campaign Identification Label.

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

Each "Campaign Identification Label" is to be located on the radiator core support in an area which will be visible when the vehicle is brought in by the customer for periodic servicing. When installing the Campaign Identification Label, be sure to pull the tab to allow adhesion of the clear protective covering. Additional Campaign Identification Labels can be obtained from Dealer Support Materials by calling 1-888-414-6322 (Monday-Friday, 8:00 a.m. to 5:00 p.m. EST). Ask for Item Number S-1015 when ordering.

Apply the "Campaign Identification Label" only on a clean, dry surface.

Submit a Product Campaign Claim with the information indicated below. Refer to the General Motors Corporation Claims Processing Manual for details on Product Campaign Claim Submission.

Dear Chevrolet/GMC Customer:

This notice is sent to inform you of a recall campaign that includes your vehicle.

General Motors has decided that certain 1998 Chevrolet and GMC M vans may have been built using the incorrect vehicle speed sensor calibration file. Vehicles with a 3.23 gear ratio axle will indicate a vehicle speed 5.47% slower than the actual vehicle speed and the odometer will accumulate 5.47% less miles than the vehicle actually traveled. Vehicles with a 3.42 gear ratio axle will indicate a vehicle speed 5.85% faster than the actual vehicle speed and the odometer will accumulate 5.85% more miles than the vehicle actually traveled.

To correct this condition, your dealer will reprogram the vehicle control module and adjust the odometer to reflect the correct mileage. This service will be performed for you at no charge .

Please contact your Chevrolet/GMC dealer as soon as possible to arrange a service date. Instructions for making this correction have been sent to your dealer. Please ask your dealer if you wish to know how much time will be needed to schedule, process and repair your vehicle.

If you experience any trouble scheduling your vehicle or you have any questions regarding this recall action, please contact the appropriate Customer Assistance Center at the number listed below:

The enclosed 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 postage paid reply card and returning it to us.

Your dealer will provide you with shuttle service or some other form of courtesy transportation while your vehicle is at the dealership 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 continued satisfaction with our products.

Chevrolet/Pontiac-GMC Divisions

General Motors Corporation