GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2008 🢒 TopKick C-Series (Conventional) C4/C5 🢒 Engine 🢒 Engine Controls and Fuel - 8.1L 🢒 Speed Calibration Programming

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 axle ratio is changed.

The Speed Calibration information must be retrieved before performing the Speed Calibration Programming. Perform the Retrieving Speed Calibration Information from the Control Module and the Speed Calibration Programming procedures 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 customer's concern.

Ensure the following conditions are met before programming a control module:

    • Vehicle system voltage
       - 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.
   • Twilight sentinel
   • Interior lights
   • Daytime running lights (DRL)--Applying the parking brake, on most vehicles, disables the DRL system. Refer to the Owner's Manual.
   • HVAC systems
   • 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.
       - RS-232
       - The connection at the data link connector (DLC)
       - 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.

  1. Turn OFF the ignition.
  2. Install the Tech 2® to the data link connector (DLC) and turn ON.
  3. Turn ON the ignition, with the engine OFF.
  4. Turn OFF all vehicle accessories.
  5. Select Diagnostics.
  6. Finish identifying the vehicle configuration as requested by the Tech 2®.
  7. Select Powertrain.
  8. Finish identifying the powertrain configuration as requested by the Tech 2®.
  9. Select Special Functions.
  10. Select Engine Output Controls.
  11. Select Speed Cal. Reprogramming.
  12. Select Read Speed Calibration.
  13. Record the Axle Ratio and Tire Revolutions Per Mile.

Speed Calibration Programming
  1. Select Service Programming System with the Tech 2®.
  2. Select Request Info.
  3. Select Continue.
  4. Select Request Info.
  5. Identify the vehicle information as requested by the Tech 2®.
  6. Select Continue.
  7. Verify the displayed VIN with the vehicle VIN. If the displayed VIN does not match the actual VIN, write down the actual VIN and correct the VIN at the Techline® terminal.
  8. Turn OFF the Tech 2® and disconnect the Tech 2® from the vehicle.
  9. Turn OFF the ignition.
  10. Connect the Tech 2® to the Techline® terminal via the RS-232 cable and turn ON.
  11. Select the Service Programming System at the main screen of the Techline terminal.
  12. Highlight the following information on the Select Diagnostic Tool and Programming Process screen:
    13. • Tech 2®, under the Select Diagnostic Tool heading
    • Vehicle, under the Select ECU Location heading
    • Reprogram ECU or Replace and Program ECU, under the Select Programming Process heading. This is depending on whether an existing module is being reprogrammed or a module is being replaced with a new one.
  13. Select Next.
  14. Ensure all steps are completed on the Preparing For Communication screen and select Next.
  15. Verify the VIN is correct and select Next.
  16. Select Speed Calibration under the Select Controller heading.
  17. Select Normal under the Select Programming Type heading and select Next.
  18. Select Next.
  19. Select Next.
  20. After the download is complete, turn OFF the Tech 2®.
  21. Disconnect the Tech 2® from the Techline® terminal.
  22. Install the Tech 2® to the DLC.
  23. Turn ON the Tech 2®.
  24. Turn ON the ignition, with the engine OFF.

    25. Important: DO NOT go into Service Programming Systems at this point.

  25. Select Diagnostics.
  26. Finish identifying the vehicle configuration as requested by the Tech 2®.
  27. Select Powertrain.
  28. Finish identifying the powertrain configuration as requested by the Tech 2®.
  29. Select Special Functions.
  30. Select Engine Output Controls.
  31. Select Speed Cal. Reprogramming.
  32. Select Reprogram Speed Calibration.

    33. Important: This procedure will allow the user to change the speed calibration for the vehicle. This procedure should only be done when a new control module has been installed or when the axle ratio or tire size has been changed.

  33. Select Done to continue.
  34. Enter the axle ratio using the F0 through F9 keys on the Tech 2® key pad.
  35. Select Done.
  36. Enter the tire revolutions per mile using the F0 through F9 keys on the Tech 2® key pad.
  37. Select Done.
  38. At this point, all entered information can be verified. Select Previous and the input information can be changed.
  39. If the information entered is correct, select Reprogram and the Tech 2® will indicate Reprogramming Successful.
  40. Select Restart if the Speed Calibration still needs to be changed. The axle ratio and tire revolutions per mile can be re-entered without reconnecting to the Techline® terminal.
  41. Select Done.
  42. 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.
  43. Start the vehicle and test drive.