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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 94 (HVAC Systems - Automatic) >> Diagnostic Information and Procedures >> Too Cold in Vehicle - Auxiliary (VIN 6) >> Test Description

Test Description

WARNING: This page is about a different car, the 2002 Oldsmobile Bravada, 2002 GMC Envoy XL, 2002 GMC Envoy, and 2002 Chevrolet TrailBlazer. However, it is still accessible from the selected car via links, so may be relevant.

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

  1. 16:  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 Cold in Vehicle - Auxiliary (VIN 6)

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 heating is insufficient.
1 Did you perform the HVAC Diagnostic System Check? Go to Step 2  Go to Diagnostic System Check - HVAC Systems - Automatic 
2
  1. Recalibrate actuators. Refer to Re-Calibrating Actuators (Primary) Re-Calibrating Actuators (Auxiliary HVAC) .
  2. Turn ON the ignition, with the engine OFF.
  3. 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
  1. With a scan tool, observe the Rear Temp. Select Sw. parameter in the Rear HVAC/RSA data list.
  2. Press the auxiliary temperature switch UP and DOWN
Does the scan tool indicate the Rear Temp. Select Sw. parameter change with each command?		 Go to Step 4  Go to Step 15 
4
  1. Turn ON the ignition, with the engine OFF.
  2. 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 3) 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 3) Blower Motor Malfunction - Auxiliary (Body Type VIN 6) 
6
  1. Start the engine.
  2. Place the mode switch in the Panel position.
  3. Place the A/C request switch in the OFF position.
Does the A/C compressor operate?		 Go to HVAC Compressor Clutch Does Not Disengage  Go to Step 7 
7 Perform the Heating Performance Diagnostic. Refer to HEATING PERFORMANCE DIAGNOSTIC in Heating, Ventilation and Air Conditioning.
Did you find and correct the condition?		 Go to Step 18  Go to Step 9 
8
  1. Turn ON the ignition, with the engine OFF.
  2. Place the auxiliary blower motor switch in the Rear position.
  3. With a scan tool, observe the Air Mix Door Actual parameter in the Rear HVAC/RSA data list.
  4. 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 9  Go to Step 15 
9
  1. Turn ON the ignition, with the engine OFF.
  2. Place the auxiliary air temperature switch to the warmest position.
  3. Start the engine.
  4. Allow the engine to reach its normal operating temperature.
  5. Feel the inlet and outlet hoses of the coolant bypass valve.
Does the inlet hose feel as warm as the outlet hose of the coolant bypass valve?		 System OK Go to Step 10 
10
  1. Turn OFF the engine.
  2. Disconnect the electrical connector of the coolant bypass valve.
  3. Turn ON the ignition, with the engine OFF.
  4. Connect a test lamp between the coolant bypass solenoid control circuit and the ground circuit of the coolant bypass valve.
  5. With a scan tool, command the Water Valve ON and OFF.
Does the test lamp illuminate with each command?		 Go to Vacuum Control System Diagnostic  Go to Step 11 
11
  1. Connect a test lamp between the coolant bypass solenoid control circuit of the coolant bypass valve and a good ground.
  2. With a scan tool, command the Water Valve ON and OFF.
Does the test lamp illuminate with each command?		 Go to Step 13  Go to Step 12 
12 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 WIRING REPAIRS in Wiring Systems.
Did you find and correct the condition?		 Go to Step 18  Go to Step 14 
13 Repair the ground circuit of the coolant bypass valve. Refer to WIRING REPAIRS in Wiring Systems.
Did you complete the repair?		 Go to Step 18  -
14 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 18  Go to Step 16 
15 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 18  Go to Step 17 
16  Replace the HVAC control module. Refer to HVAC Control Module Replacement .
Did you complete the replacement?		 Go to Step 18  -
17 Replace the auxiliary HVAC control module. Refer to HVAC Control Module Replacement - Auxiliary .
Did you complete the replacement?		 Go to Step 18  -
18 Operate the system in order to verify the repair.
Did you correct the condition?		 System OK Go to Step 2 
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