The Speed Calibration Programming must be done when any of the following procedures are performed:
| • | The control module is replaced. |
| • | The tire size is changed. |
| • | The gear ratio is changed. |
If the control module is being replaced, the Speed Calibration information must be retrieved before replacing the control module. Perform the Retrieving Speed Calibration Information from the Control Module and the Speed Calibration Programming During
Control Module Programming procedures listed below.
If the control module is not being replaced, a shorter procedure can be used to perform Speed Calibration Programming. Perform the Speed Calibration Programming without Control Module Programming procedure listed below.
Before Programming a Control Module
Important: DO NOT program a control module unless you are directed by a service procedure or you are directed by a General Motors Corporation service bulletin. Programming a control module at any other time will not permanently
correct a customers concern. If the control module is being replaced the Speed Calibration also be programmed.
Ensure the following conditions are met before programming a control module:
| - | There is no charging system concern. All charging system concerns must be repaired before programming a control module. |
| - | Battery voltage is greater than 12 volts but less than 16 volts. The battery must be charged before programming the control module if the battery voltage is low. |
| - | A battery charger is NOT connected to the vehicle's battery. Incorrect system voltage or voltage fluctuations from a battery charger, may cause programming failure or control module damage. |
| - | Turn OFF or disable any system that may put a load on the vehicle's battery. |
| • | Daytime running lights (DRL)--Applying the parking brake, on most vehicles, disables the DRL system. Refer to the Owners Manual. |
| • | Engine cooling fans, etc. |
| • | The ignition switch is in the proper position. The scan tool 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. |
| • | All tool connections are secure. |
| - | The connection at the data link connector (DLC) is secure. |
| - | Voltage supply 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. |
Retrieving Speed Calibration Information from the Control Module
Important: Only perform this procedure if the control module is being replaced or the axle ratio or tire size has been changed. The current Axle Ratio and Tire Revolutions Per Mile can be determined with the Tech 2®.
The Axle Ratio can also be found on the Service Parts Identification (SPID) and the Tire Revolutions Per Mile can be obtained from the tire manufacturer as follows:
- Using the Tech 2®, select Module Setup/Speed Calibration Programming.
- Select Read Speed Calibrations.
- Record the Axle Ratio and Tire Revolution per Mile.
Speed Calibration Programming without Control Module Programming
- Using the Tech 2®, select Module Setup/Speed Calibration Programming.
- Select Speed Reprogramming/Reprogram Speed Calibration.
- Record the Axle Ratio and Tire Revolution per Mile.
- Using the soft keys, enter the Axle Ratio and then the Tire Revolution per Mile.
- Verify all entered information.
- If all entered information is correct, Start Reprogramming.
- Turn OFF the ignition and allow the control module to power down. This time should be at least 30 seconds. The Tech 2 may beep when the control module stops communicating.
- Start the vehicle and test drive.
Speed Calibration Programming During Control Module Programming
Important: The Capture Info function on the scan tool will store the Speed Calibration. To restore the speed calibration, the Restore Info function on the scan tool must be performed.
- If the Capture Info feature was not used, refer to Speed Calibration Programming without Control Module Programming in this section.
- Turn OFF the ignition and allow the control module to power down. This time should be at least 30 seconds. The Tech 2® may beep when the control module stops communicating.
- Start the vehicle and test drive.
