GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2001 🢒 GMC C Sierra - 2WD 🢒 HVAC 🢒 HVAC Systems - Automatic 🢒 Too Hot in Vehicle

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. The DTCs listed may set, if there is a concern with the actuator, when a calibration of the actuators is performed.

    2.

  2. Ambient air temperature must be above 3°C (38°F) in order for this A/C compressor test to be run.

    3.

  3. Misaligned air baffles will cause poor A/C performance at idle and low speed operation.

    4.

  4. The specified values are from the A/C System Performance Test.

    5.

  5. This action ensures that the internal fan of the inside air temperature sensor assembly is providing air flow across the internal sensor.

Step

Action

Values

Yes

No

Schematic Reference: HVAC Schematics

DEFINITION: Temperature can not be adjusted, or cooling 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

Important: If during this diagnostic procedure the HVAC control module is disconnected a recalibration of actuators must be performed to avoid misdiagnosis.

  1. Recalibrate actuators. Refer to Actuator Recalibration .
  2. Turn ON the ignition, with the engine OFF.
  3. Observe the Diagnostic Trouble Code (DTC) List in Heating and Air Conditioning.

Does the scan tool display any DTC B0229, B0414, B0434 or B3761?

--

Go to Diagnostic Trouble Code (DTC) List

Go to Step 3

3

Important:: Ambient air temperature must be above 3°C (38°F).

  1. Cover the sunload sensor.
  2. Start the engine.
  3. Fully open all panel outlets.
  4. Adjust the temperature control to maximum cooling.
  5. Select PANEL (upper) mode.
  6. Adjust the blower speed to maximum.
  7. Ensure that the VENT (outside air) mode indicator is not illuminated.

Does the A/C compressor operate?

--

Go to Step 4

Go to HVAC Compressor Clutch Does Not Engage

4

Inspect the air baffles for proper installation. Refer to Radiator Air Baffle Assemblies and Deflectors in Engine Cooling.

Did you find and correct the condition?

--

Go to Step 25

Go to Step 5

5

Does the blower operate and provide sufficient air flow?

--

Go to Step 6

Go to Blower Motor Malfunction

6

Perform the refrigerant system performance test. Refer to Air Conditioning (A/C) System Performance Test .

Did the system pass the A/C System Performance Test?

--

Go to Step 7

Go to Air Conditioning (A/C) System Performance Test in Heating, Ventilation and Air Conditioning

7

Check the air temperature sensors for proper installation.

Refer to the following procedures:

Did you find and correct the condition?

--

Go to Step 25

Go to Step 8

8

  1. Start the engine.
  2. Fully open all panel outlets.
  3. Adjust the temperature control to maximum cooling.
  4. Ensure that the VENT (outside air) mode indicator is not illuminated.
  5. Inspect for air flow through the inside air temperature sensor by placing a 5 cm (2 in) square piece of paper over the sensor air outlet.

Does the paper stay in place?

--

Go to Step 9

Go to Step 13

9
  1. Turn the engine OFF.
  2. Install a scan tool.
  3. Cover the sunload sensor.
  4. Start the engine.
  5. Adjust driver side temperature to 22°C (74°F).
  6. With a scan tool, observe the Solar Sensor data parameter in the Heating and Air Conditioning data list.

Does the scan tool indicate that the solar sensor parameter is greater than the specified value?

230  Counts

Go to Step 10

Go to Step 19

10
  1. Uncover the sunload sensor.
  2. Direct a light source at the sunload sensor.

Do the counts change?

--

Go to Step 11

Go to Step 19

11
  1. Install a thermometer near the inside air temperature sensor.
  2. With a scan tool, observe the Inside Air Temp parameter in the Primary ECC Data list.

Does the scan tool indicate sensor temperature is within 3°C (5°F) of the thermometer temperature?

--

Go to Step 12

Go to Step 16

12
  1. Turn ON the ignition, with the engine OFF.
  2. Observe the Upper Outlet Temp. and the Lower Outlet Temp. parameter in the Primary ECC Data list.
  3. Turn OFF the ignition.
  4. Measure the resistance of the upper and the lower air temperature sensors. Refer to Sensor Resistance Table .
  5. Compare the resistance of the sensor to the count value of the scan tool.

Does the resistance measure near the sensor resistance table value?

--

System OK

Go to Step 18

13

Inspect for a blocked or malfunctioning inside air temperature sensor.

Did you find and correct the condition?

--

Go to Step 25

Go to Step 14

14

Test the ignition 1 voltage circuit of the inside air temperature sensor for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 25

Go to Step 15

15

Test the ground circuit of the inside air temperature sensor for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 25

Go to Step 17

16
  1. Turn OFF the ignition.
  2. Test the inside air temperature sensor resistance. Refer to Sensor Resistance Table .

Does the resistance measure near the specified value?

--

Go to Step 20

Go to Step 17

17

Inspect for poor connections at the harness connector of the inside air temperature sensor. 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 25

Go to Step 23

18

Inspect for poor connections at the harness connector of the upper and lower air temperature sensors. 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 25

Go to Step 21

19

Inspect for poor connections at the harness connector of the sunload sensor. 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 25

Go to Step 22

20

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 25

Go to Step 24

21

Replace the suspect air temperature sensor. Refer to one of the following procedures:

Did you complete the replacement?

--

Go to Step 25

--

22

Replace the sunload sensor. Refer to Sun Load Sensor Replacement .

Did you complete the replacement?

--

Go to Step 25

--

23

Replace the inside air temperature sensor. Refer to Inside Air Temperature Sensor Replacement .

Did you complete the replacement?

--

Go to Step 25

--

24

Important:: Perform the recalibration procedure for the HVAC control module.

Replace the HVAC control module. Refer to HVAC Control Module Replacement .

Did you complete the replacement?

--

Go to Step 25

--

25

Operate the system in order to verify the repair.

Did you correct the condition?

--

System OK

Go to Step 3