Test Description

WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 2004 Oldsmobile Bravada, 2004 GMC Envoy XUV, 2004 GMC Envoy XL, 2004 GMC Envoy, and 2004 Chevrolet TrailBlazer. However, it is still accessible from the selected car via links, so may be relevant.

The numbers below refers to the step number in the diagnostic table.

7: To request A/C operation the primary HVAC controls must be set to enable the A/C compressor.
11: If the test light remains illuminated the answer is No.
19: The primary HVAC control module controls the coolant bypass valve. It receives a Class 2 message from the auxiliary HVAC control module for the proper position of valve.

Too Hot in Vehicle - Auxiliary

Step	Action	Yes	No
Schematic Reference: HVAC Schematics Connector End View Reference: HVAC Connector End Views DEFINITION: The auxiliary temperature cannot be adjusted, or the auxiliary cooling is insufficient during A/C operation.
1	Did you perform the HVAC Diagnostic System Check?	Go to Step 2	Go to Diagnostic System Check - HVAC Systems - Automatic
2	Recalibrate actuators. Refer to Re-Calibrating Actuators (Primary) or Re-Calibrating Actuators (Auxiliary HVAC) . Turn ON the ignition, with the engine OFF. With a scan tool, observe the DTC list in Rear HVAC/RSA. Does the scan tool display DTC B0145, B0428, or B3531?	Go to Diagnostic Trouble Code (DTC) List	Go to Step 3
3	With a scan tool, observe the Rear Temp. Select Sw. parameter in the Rear HVAC/RSA data list. Rotate the auxiliary air temperature switch from the coldest position to the warmest position. Does the scan tool indicate the Rear Temp. Select Sw. parameter increase from 1 to 13 Counts?	Go to Step 4	Go to Step 18
4	Turn ON the ignition, with the engine OFF. Place the auxiliary blower motor switch in each speed position. Does the auxiliary blower motor operate in any of the speed positions?	Go to Step 5	Go to Blower Motor Inoperative - Auxiliary (Body Type VIN 6)
5	Does the auxiliary blower motor operate at the desired speed?	Go to Step 6	Go to Blower Motor Malfunction - Auxiliary (Body Type VIN 6)
6	Does the customer concern occur when the A/C is OFF?	Go to Step 9	Go to Step 7
7	IMPORTANT: Ambient air temperature must be above 3°C (36°F). Start the engine. Place the blower motor switch in the maximum speed position. Place the A/C request switch in the ON position. Place temperature switch in the coldest position. Does the A/C compressor operate?	Go to Step 8	Go to HVAC Compressor Clutch Does Not Engage
8	Perform the refrigerant system performance test. Refer to Air Conditioning (A/C) System Performance Test in Heating, Ventilation and Air Conditioning. Did you find and correct the condition?	Go to Step 21	Go to Step 9
9	Turn ON the ignition, with the engine OFF. Place the auxiliary blower motor switch in the Rear position. With a scan tool, observe the Air Mix Door Actual parameter in the Rear HVAC/RSA data list. Place the auxiliary air temperature switch from the coldest position to the warmest position. Does the Air Mix Door Actual parameter counts change?	Go to Step 10	Go to Step 19
10	Turn ON the ignition, with the engine OFF. Place the auxiliary air temperature switch to the coldest position. Start the engine. Allow the engine to reach its normal operating temperature. Feel the inlet and outlet hoses of the coolant bypass valve. Does the inlet hose feel warmer than the outlet hose of the coolant bypass valve?	System OK	Go to Step 11
11	Turn OFF the engine. Disconnect the electrical connector of the coolant bypass valve. Turn ON the ignition, with the engine OFF. Connect a test lamp between the coolant bypass solenoid control circuit and the ground circuit of the coolant bypass valve. With a scan tool, command the Water Valve ON and OFF. Does the test lamp illuminate on and off with each command?	Go to Vacuum Control System Diagnostic	Go to Step 12
12	Does the test lamp remain illuminated when commanded to OFF?	Go to Step 15	Go to Step 13
13	Connect a test lamp between the coolant bypass solenoid control circuit of the coolant bypass valve and a good ground. With a scan tool, command the Water Valve ON and OFF. Does the test lamp illuminate with each command?	Go to Step 16	Go to Step 14
14	Test the coolant bypass solenoid control circuit of the coolant bypass valve for one of the following conditions: A short to ground A high resistance An open Refer to Circuit Testing and to Wiring Repairs in Wiring Systems. Did you find and correct the condition?	Go to Step 21	Go to Step 17
15	Test the coolant bypass solenoid control circuit of the coolant bypass valve for a short to voltage. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems. Did you find and correct the condition?	Go to Step 21	Go to Step 18
16	Repair the ground circuit of the coolant bypass valve. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair?	Go to Step 21	-
17	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 in Wiring Systems. Did you find and correct the condition?	Go to Step 21	Go to Step 19
18	Inspect for poor connections at the harness connector of the auxiliary HVAC control module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition?	Go to Step 21	Go to Step 20
19	Replace the HVAC control module. Refer to HVAC Control Module Replacement . Did you complete the replacement?	Go to Step 21	-
20	Replace the auxiliary HVAC control module. Refer to HVAC Control Module Replacement - Auxiliary . Did you complete the replacement?	Go to Step 21	-
21	Operate the system in order to verify the repair. Did you correct the condition?	System OK	Go to Step 2