TECH 1 REVISED ODOMETER RECALIBRATION PROCEDURE

SUBJECT: REVISED ODOMETER RECALIBRATION PROCEDURE

VEHICLES AFFECTED: ALL 1990-"Y"'--CARS

This bulletin serves to update information concerning Corvette CCM EEPROM reprogramming using the Tech 1 1990 CHEVROLET EEPROM SERVICE CARTRIDGE. This reprogramming process must take place when installing a new service CCM into a 1990 Corvette.

When programming the new CCM, odometer information is required during the procedure. The odometer information from the vehicle can be entered into the Tech 1 in either miles or kilometres. However, an error exists in the kilometres-to-miles conversion in the Tech 1 cartridge.

Use the following procedure when programming a service CCM to ensure the downloaded odometer information is correct.

Tech 1 Odometer Downloading Procedure

1. If the CCM is still in the vehicle, turn the ignition "ON" and read the odometer information on the Instrument Panel Cluster (IPC). If the IPC information is in kilometres, press the ENG/MET button on the Drive Infor- mation Centre (DIC) to change the odometer display to miles.

2. If the CCM is not in the vehicle, or the odometer information is unreadable or inaccurate, use the following equation to convert the odo- meter kilometre information to miles:

Kilometres divided by 1.609 = Miles

3. After entering the VIN and option content information into the Tech 1 during the programming process, the technician will be prompted for odometer information at the following screen:

ODOMETER SELECT YES = MILES NO = KILOMETRES (YES/NO)

4. Select YES at that screen for miles, then enter either the mileage infor- mation from the IPC display, or the mileage information obtained from the kilometres-to-miles conversion equation shown in Step 2.

5. After technician confirmation that the odometer information is correct, the programming procedure will take place. The procedure will take from 5-15 seconds. After the programming procedure is complete, confirm that the correct odometer information is displayed on the IPC when the CCM is installed in the vehicle.

Corvette CCM - Reprogramming Mileage Accuracy

The odometer reading on the Corvette IPC will be within 0-15 miles (0-24 kilometres) of the odometer value that the technician entered into the Tech 1 during the programming procedure. THE CCM STORES THE ODOMETER VALUE IN 16-MILE INCREMENTS.

1990 CHEVROLET EEPROM SERVICE CARTRIDGE Usage With Tech 1 Units With Serial Numbers of 2000 or Less

The 1990 CHEVROLET EEPROM SERVICE CARTRIDGE will not operate in Tech 1 units that have serial numbers less than 86020 02000 (the first 2000 units). Check the serial number plate on the back of the Tech 1 unit.

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.