Service Update for Inventory Vehicles Only-Vehicle Quality Drive Audit-Expires October 31, 2008

THIS BULLETIN IS BEING REVISED TO EXTEND THE EXPIRATION DATE. PLEASE DISCARD ALL COPIES OF BULLETIN 08187B, ISSUED AUGUST 2008.

THIS SERVICE UPDATE INVOLVES EARLY PRODUCTION VEHICLES IN DEALER INVENTORY ONLY AND WILL EXPIRE OCTOBER 31, 2008.

This bulletin provides a procedure to conduct a vehicle quality drive audit on certain, early production 2008 model year Chevrolet Tahoe and GMC Yukon Two-Mode Hybrid vehicles. A successful launch of these innovative, advanced technology vehicles is very important to our future. Many of these vehicles have been in storage for an extended period of time. In order to assure maximum customer enthusiasm, a special Vehicle Quality Drive Audit procedure has been developed. The intent of this procedure is to identify concerns related to extended storage and other customer dissatisfiers, so that they can be corrected before sale. We recommend that this procedure be completed by the hybrid technician or service personnel who are trained and familiar with the Two-Mode Hybrid Tahoe or Yukon. Identification and correction of any concerns prior to delivery will promote maximum customer enthusiasm for these important new technology vehicles.

This procedure should be completed on involved vehicles currently in dealership inventory as soon as possible, but no later than October 31, 2008, at which time this bulletin will expire.

A list of involved vehicles currently in dealer inventory is available on the "Service Update Bulletin Information" link under the "Service" tab in DealerWorld (GM US), or attached to the Dealer Communication (Canada), used to release this bulletin.

Important: Dealers are to confirm vehicle eligibility prior to beginning repairs by using the system below. Not all vehicles within the above breakpoints may be involved.

We recommend that this procedure be completed by the hybrid technician or service personnel who are trained and familiar with the Two-Mode Hybrid Tahoe or Yukon.

Perform PDI using the Hybrid PDI form.

Add 8 gallons (30 litres) of fuel to the vehicle.

Check GM Vehicle Inquiry System (GMVIS) for any open recalls or service updates, including Service Update 08119A.

If any MILs are illuminated, the vehicle must be repaired prior to proceeding with the quality drive.

Secure proper plate and documentation for 75 mile (120 kilometer) quality road test audit.

Check rear hatch closing efforts.

Document technician ID and starting mileage on repair order.

Start vehicle and allow it to warm up.

Set compass, radio stations, and select hybrid display on NAV screen, and set the Driver Information Center (DIC) to "Instant Fuel Economy".

Record the tire pressures that are displayed on the DIC.

Verify control operations; windows, RKE, power seats, wipers, power mirrors, and cycle sunroof, if equipped.

Proceed with the road test quality drive, which will be a mix of city and highway driving.

OBEY ALL TRAFFIC LAWS, WEAR SAFETY BELTS, AND BE AWARE OF SURROUNDINGS, TRAFFIC AND PEDESTRIANS ETC., AND DO NOT DRIVE DISTRACTED.

Mute the radio. The Hybrid display screen on NAV radio needs to be ON. Proceed with the drive under light throttle accelerations until Auto Stop is achieved.

Proceed with light acceleration from a stop in electric drive. This can be observed on the Hybrid display screen. This electric propulsion needs to be done a minimum of three times.

Decelerate lightly from 40-45 MPH (65-72 km/h) and verify regenerative braking mode and charging of the hybrid battery.

Accelerate from a stop to approximately 50 MPH (80 km/h) at half throttle. This should be done a minimum of three times.

Brake moderately to ensure that any surface corrosion is removed from the brake rotors.

Proceed to the highway portion of the drive.

Drive at various highway and freeway speeds observing the DIC instantaneous fuel economy mode. For a portion of the drive try to stay in 4-cylinder mode or "Green" in the efficiency gage.

Use the cruise control "set", "decel", and "accel" modes.

Vary climate control, including "A/C", "Temp" and modes.

Accelerate aggressively to get a downshift at highway speeds.

When conditions allow, perform heavy acceleration (WOT) from a stop up to 50 MPH (80 km/h) and note the shift feel. This should be done a minimum of three times.

When returning to the dealership, back out of a parking spot several times under light throttle.

Caution: The vehicle must be on dealer property for this next maneuver.

Secure an area at the dealership where the vehicle can be brake torqued in reverse; by firmly depressing the brake pedal with your left foot to prevent vehicle movement or tire slippage, and applying approximately 75% throttle with your right foot for 5 seconds. Release the throttle and allow the engine to return to idle. Drive forward 15 feet (4.6 meters) and repeat this maneuver three times.

Reset the average fuel mileage, and trip mileage on the DIC.

Document any issues on the repair order including ending mileage. Any repairs must be completed by the hybrid technician.

For vehicles subjected to this quality audit drive, use:

A warranty claim should be submitted for repair of any issues identified.