Rear HVAC ticking noise, no rear temperature or mode control, DTC B0434 / B3764 (revised auxiliary HVAC control module)

Applies toThe article concerns some 2003-06 Cadillac Escalade, Chevrolet Suburban and Tahoe, and GMC Yukon models with RPO CJ2 and C69.

Owners of some 2003-06 Cadillac Escalade, Chevrolet Suburban and Tahoe, and GMC Yukon models with RPO CJ2 and C69 may have one or more of the following concerns:— [1]

First signsThe concerns are an intermittent ticking or clicking noise from the rear HVAC system, being unable to control the rear system temperature, and being unable to change the rear system modes.

- Intermittent ticking/clicking noise from rear HVAC system - Unable to control rear system temperature - Unable to change rear system modes— [1]

First signsA defaulted door stays at the default position until the code is cleared; clearing the code lets it operate properly until overtravel occurs again.

When a system door defaults, that door stays at the default position until the code is cleared. Clearing the code allows the door to operate properly until the overtravel condition re-occurs.— [1]

Why it happensThe HVAC actuators may hunt for the correct commanded position, and this cycling can cause a clicking or ticking noise.

The HVAC actuators may hunt for the correct commanded position. This cycling can cause a clicking or ticking noise.— [1]

Why it happensOvertravel of the HVAC system control doors can cause the listed conditions; when it occurs a DTC sets and the door goes to a preset default position.

Overtravel of the HVAC system control doors can cause one or more of the listed system conditions. If overtravel occurs, a DTC sets and the door goes to a preset default position.— [1]

How to confirmThe overtravel DTCs are B0434 for the auxiliary (rear) temperature door and B3764 for the auxiliary (rear) mode door.

B0434 Auxiliary (rear) temperature door B3764 Auxiliary (rear) mode door— [1]

RepairReplace the auxiliary (rear) HVAC control module; it contains a new calibration that compensates for the actuator overtravel and the hunting, clicking and ticking noises.

Replace the auxiliary (rear) HVAC control module (part number listed in the table below). This module contains a new calibration to compensate for the actuator overtravel condition and the hunting/clicking and ticking noises.— [1]

RepairFor all 2003-06 with CJ2 and C69, the auxiliary HVAC control module is part number 15832319.

All 2003-06 with CJ2 and C69 Module, Auxiliary HVAC control 15832319— [1]

RepairThe second design rear blower control module is 89024926 for Tahoe, Yukon and Escalade (short wheelbase) and 89018846 for Suburban, Yukon XL and Escalade ESV (long wheelbase).

Tahoe, Yukon, Escalade (short wheelbase) Second design rear blower control module 89024926 Suburban, Yukon XL, Escalade ESV (long wheelbase) Second design rear blower control module 89018846— [1]

CautionWith the new module the rear blower speed may rise slightly (approximately 50 rpm); if the customer objects, the blower control module may be replaced with the second design blower control module.

When using the new auxiliary HVAC control module, you may notice a slight increase in rear blower speed (approximately 50 rpm). If the customer comments that the increase in blower speed is objectionable, the blower control module may be replaced with the second design blower control module to correct the slight increase in blower speed.— [1]

CautionDo not use the revised auxiliary HVAC control module unless one or more of the listed codes is set; it will not correct any other DTC or A/C performance concern.

TIP: The revised auxiliary HVAC control module should not be used unless one or more of the codes listed above is set. The revised control module will not correct any other DTC or A/C performance concern.— [1]