Difficult to Maintain Desired HVAC Temperature, HVAC Blower Noisy (Update HVAC Calibrations with Tech 2)

This bulletin is being revised to update the models information with a statement that the bulletin only applies to vehicles with automatic HVAC. Please discard Corporate Bulletin Number 03-01-39-006A (Section 01 -- HVAC).

Some customers may comment that it is difficult to maintain the desired HVAC temperature. The HVAC system over shoots the desired temperature and blows air that transitions from too hot, to too cold, onto the occupants. The system does settle into the desired temperature after a period of searching. The blower may be noisy and the fan runs at a speed higher than desired. It has also been found that the HVAC system may cycle rapidly between air delivery modes (for example, floor to bilevel to floor).

A procedure using the Tech 2® has been developed to update the Instrument Panel Module (IPM) calibrations for all vehicles listed above. In addition to the IPM update, the Seville and DeVille models MUST also perform an update to the HVAC calibration within the Dash Integration Module (DIM). Use the following procedures.

Important: The Tech 2® must contain the NAO software version 25.001 or later.

1. Install the Tech 2® to the vehicle and power on.
2. Select "Diagnostic" from the menu.
3. Build the vehicle from the menu options.
4. Select "Body" from the menu.
5. Build the vehicle from the menu options.
6. Select "Instrument Panel Module (IPM)" from the menu.
7. Select "Special Functions" from the menu.
8. Select "Miscellaneous Test" from the menu.
9. Select "IPM Recalibration" from the menu.
10. A message will appear after the reprogram has been successfully completed.

1. Install the Tech 2® to the vehicle and power on.
2. Select "Diagnostic" from the menu.
3. Build the vehicle from the menu options.
4. Select "Body" from the menu.
5. Build the vehicle from the menu options.
6. Select "Dash Integration Module (DIM)" from the menu.
7. Select "Special Functions" from the menu.
8. Select "Update HVAC Cals. in DIM" from the menu.
9. A message will appear after the reprogram has been successfully completed.

For vehicles repaired under warranty, use: