HVAC System Inoperative for a Drive Cycle, Poor HVAC System Performance in High Ambient Temperatures (Update HVAC Control Module Software)

This bulletin is being revised to correct the RPO usage information below:

RPO CJ2 = HVAC System Air Conditioner Front, Automatic Temperature Control, Auxiliary Temperature Control

RPO CJ3 = HVAC System Air Conditioner Front, Manual Temperature Control, Auxiliary Temperature Control

Please discard Corporate Bulletin Number 02-01-39-005 (Section 01 -- HVAC).

Some customers may comment about no cold air from the heating, ventilation and air conditioning (HVAC) system during a drive cycle. This concern may occur at any time during the drive cycle and at any temperature setting. The HVAC system operation returns to normal after the vehicle has been keyed to off and restarted. This concern is intermittent and most likely to occur on hot days. This concern may be found on vehicles equipped with manual (CJ3) and automatic (CJ2) HVAC systems. Other customers may comment about poor HVAC system performance in high ambient temperature conditions. This concern may be present in automatic (CJ2) HVAC systems only. An HVAC control module software update was put into all production vehicles beginning in September 2002. Vehicles built in September 2002 and earlier may need this software update.

Update the HVAC control module using software available through GM Access beginning September 9, 2002. The update will be fully available October 7, 2002 to all dealers on TIS 2000 CD version 10. This software update addresses both the intermittent no cooling and the poor performance concerns. If the software update does not correct the concerns, perform the HVAC Diagnostic System Check and repair as necessary. If the HVAC control module is replaced with a part from GMSPO, make sure the module has the latest software update. The module may need to be updated even though it is a new part.

For vehicles repaired under warranty, use: