| Subject: | Information On HVAC Control Module Lockup During Reprogramming |
| Models: | 2007 Cadillac Escalade Models |
| 2007 Chevrolet Avalanche, Silverado, Suburban, Tahoe |
| 2007 GMC Sierra, Yukon Models |
| with Automatic Temperature Control HVAC System (RPO CJ2) |
The purpose of this bulletin is to alert technicians to a condition they may encounter while trying to reprogram a Heating, Ventilation and Air Conditioning (HVAC) control module. If the HVAC control module reprogramming event is interrupted, the control
module may go into a "lock up" mode. This will cause the HVAC control module to disable communications and a second try at reprogramming will fail. The interruption may be caused by a software anomaly inside the HVAC control module.
If the HVAC reprogramming event was interrupted and a subsequent reprogramming attempt fails, perform a battery reset. This can be accomplished by either removing and reinstalling the HVAC BATT fuse, located in the underhood fuse block, or by disconnecting
and reconnecting the HVAC control module connector C2. Connector C2 is grey in color with 16 cavities. Once the battery reset has been performed, the HVAC control module will resume communications and will then be able to be reprogrammed.
The Warranty Parts Center (WPC) has received HVAC control modules that have been returned and described as non-functional but were tested with no problems found. If the module has been replaced due to a failed second attempt at reprogramming caused by
the lock up, the module will be returned and charged back to the dealer. Technicians must also remember that after a new HVAC control module has been installed into a vehicle, it must be programmed, otherwise it will not be functional.
