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Shane, ASE Certified Technician
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2003 chevy Tahoe: just blows cold air...Help

Resolved Question:

2003 chevy Tahoe, rear heater will not blow heat when turned to the full hot just blows cold air...Help!
Submitted: 6 years ago.
Category: Chevy
Expert:  Shane replied 6 years ago.

This is a common issue here is a TSB

#06-01-39-015A: Unable to Control Rear HVAC Temperature or Modes, Intermittent Ticking Noise from Rear HVAC Actuators or Rear HVAC DTCs B0434 or B3764 (Replace Auxiliary HVAC Control Module) - (Jan 12, 2007)

Subject:Unable To Control Rear HVAC Temperature Or Modes, Intermittent Ticking Noise From Rear HVAC Actuators Or Rear HVAC DTCs B0434 Or B3764 (Replace Auxiliary HVAC Control Module)

Models:2003-2006 Cadillac Escalade Models
2003-2006 Chevrolet Suburban, Tahoe
2003-2006 GMC Yukon Models
with Automatic Control HVAC System and Rear A/C (RPOs CJ2 and C69)


This bulletin is being revised to correct one of the blower motor control module part numbers. Please discard Corporate Bulletin Number 06-01-39-015 (Section 01 -- HVAC).


Some customers may comment on one or more of the following conditions:

An intermittent ticking/clicking noise from the rear Heating, Ventilation and Air Conditioning (HVAC) system.
Unable to control rear HVAC system temperature.
Unable to change rear HVAC system modes.

Technicians may find that Diagnostic Trouble Codes (DTCs) B0434 and/or B3764 have been set.


These conditions may be caused by HVAC actuators that hunt for the correct position. This cycling may cause a clicking or ticking noise.

An overtravel of the HVAC system control doors may cause one or more of the above system conditions. If an overtravel occurs, a DTC will be set, and the door will go to a preset default position.

When a system door defaults, that door will stay at the default position until the DTC is cleared. Clearing the DTC will allow the door to operate properly until the overtravel condition reoccurs. The following table lists the DTCs that may have been set and the door that is associated with that code.

Overtravel DTC

System Door Affected


Auxiliary (rear) Air Temperature Actuator


Auxiliary (rear) Mode Actuator


Technicians are to replace the auxiliary (rear) HVAC control module with the part number listed in the table below. Refer to the Auxiliary Heater and Air Conditioning Control Module Replacement procedure in SI for more information. This module contains a new calibration to compensate for the actuator overtravel condition and the hunting/clicking noises. The new calibration effectively eliminates DTCs B0434 and B3764. The new control module also eliminates the default position of the doors associated with the DTC. The new control module will allow door travel from counts 0 to 255 without setting a DTC or defaulting the door.

The new auxiliary HVAC control module is compatible with either the first or second design blower motor control module. When using the new auxiliary HVAC control module, the customer may notice a slight increase in the rear blower motor speed (approximately 50 rpm) at a given setting, as compared to the blower motor speed at the same setting with the original HVAC control module. If the customer comments that the increase in blower speed at a given setting is objectionable, the blower motor control module may be replaced with the second design part listed below to correct the slight increase in speed.

The revised auxiliary HVAC control module should not be used unless one or both of the DTCs are set or one or more of the conditions listed above are present. The revised auxiliary HVAC control module will not correct any other DTC or Air Conditioning (A/C) performance concern.

Parts Information

Auxiliary HVAC Control Module

Part Number




Module Assembly-Auxiliary Heater & A/C Control


The blower motor control modules listed below should not be used unless the customer finds the change in blower speeds between the original and the new auxiliary HVAC control modules objectionable.

Blower Motor Control Modules

Part Number

Part Description

Vehicle Application



Module Assembly, Auxiliary Heater & A/C Control (Auxiliary Blower Motor Control Module) (Second Design)

Escalade, Tahoe, Yukon (vehicles with a short wheelbase)



Module Assembly, Auxiliary Heater & A/C Control (Auxiliary Blower Motor Control Module) (Second Design)

Escalade ESV, Suburban, Yukon XL (vehicles with a long wheelbase)


Customer: replied 6 years ago.
So is this an item thatI I can replace ? Does the fault code have to be cleared before doing so...Thanks Jim
Expert:  Shane replied 6 years ago.
Oh i should have asked this first, you have automatic climate control right? yes you can replace the module yourself, replacing the module will clear the code as the code is stored in this module. remove the rt. rear quarter panel to replace the module
Customer: replied 6 years ago.
Which module part # XXXXX be the one I should get then, the first or second design. Tahnks again Jim
Expert:  Shane replied 6 years ago.
First one for tahoe 89024926 also have your VIN handy they may also need that to order. This is a dealer only part.
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