Diagnostic Aids

WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2007 GMC Yukon XL, 2007 GMC Yukon, 2007 Chevrolet Tahoe, 2007 Chevrolet Suburban, and 2007 Chevrolet Avalanche. However, it is still accessible from the selected car via links, so may be relevant.

The condition may be intermittent. Refer to Testing for Intermittent Conditions and Poor Connections .
Inspect the air delivery system for the following conditions:
- A dirty HVAC air filter, if applicable
- An obstruction to the airflow
- Air leaks
- Misaligned air ducts
- Broken or binding linkages or doors

Air Delivery Improper

Step	Action	Value(s)	Yes	No
Schematic Reference: HVAC Schematics Connector End View Reference: HVAC Connector End Views
1	Did you perform the Diagnostic System Check - Vehicle?	-	Go to Step 2	Go to Diagnostic System Check - Vehicle
2	Turn ON the ignition, with the engine OFF. Place the blower motor switch in the OFF position. Is the blower motor OFF?	-	Go to Step 3	Go to Blower Motor Always On
3	Place the blower motor switch in each speed position. Does the blower motor operate in any of the speed positions?	-	Go to Step 4	Go to Blower Motor Inoperative
4	Does the blower motor operate in each speed position?	-	Go to Step 5	Go to Blower Motor Malfunction
5	With a scan tool, observe the Mode Select Position parameter in the Heating and Air Conditioning data list. Place the mode switch in each position. Does the scan tool indicate that the Mode Select Position parameter displays the correct mode switch positions?	-	Go to Step 6	Go to Step 7
6	Place the blower motor switch in the maximum speed position. Place the mode switch in the bi-level position. Place the recirculation switch in the ON position. Observe the drive shaft of the recirculation actuator. Place the recirculation switch in the OFF position. Does the recirculation door move from the recirculation position to the outside air position?	-	Go to Diagnostic Aids	Go to Air Recirculation Malfunction
7	Inspect for poor connections at the harness connector of the HVAC control module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition?	-	Go to Step 9	Go to Step 8
8	Replace the HVAC control module. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement?	-	Go to Step 9	-
9	Operate the system in order to verify the repair. Did you correct the condition?	-	System OK	Go to Step 2