For 1990-2009 cars

### Diagnostic Instructions

• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

• | Strategy Based Diagnosis

• | Diagnostic Procedure Instructions

### Test Description

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

1. This test resets the HVAC control module and checks for current air temperature actuator DTC.

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

Step | Action | Values | Yes | No
--- | --- | --- | --- | ---
Schematic Reference: HVAC Schematics Connector End View Reference: HVAC Connector End Views DEFINITION: The auxiliary air temperature cannot be adjusted from one or both auxiliary controls, or the auxiliary cooling is insufficient.
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle
2 | The auxiliary HVAC control module cannot request A/C compressor operation. An A/C request must be generated by the HVAC control module to provide cooled airflow through the auxiliary system. Does the HVAC control module operate and provide sufficient heating? | -- | Go to Step 3 | Go to Too Cold in Vehicle
3 |

1. Install a scan tool.
2. Turn ON the ignition, with the engine OFF.
3. Observe the current DTC list in HVAC Module using the scan tool.

Does the scan tool display DTC B0433?

--

Go to Diagnostic Trouble Code (DTC) List - Vehicle

Go to Step 4

4 | Place the auxiliary blower motor switch in each speed position. Does the auxiliary blower motor operate in each speed position? | -- | Go to Step 5 | Go to Auxiliary Blower Motor Malfunction
5 | Does the auxiliary blower motor operate at the desired speeds? | -- | Go to Step 6 | Go to Auxiliary Blower Motor Malfunction
6 | Does the Too Hot In Vehicle concern occur when A/C is desired? | -- | Go to Step 7 | Go to Step 8
7 | Perform the A/C system performance test. Refer to Air Conditioning (A/C) System Performance Test . Did you find and correct the condition? | -- | Go to Step 18 | Go to Step 8
8 |

1. Observe the Rear Temp Dr. Actual parameter in the Door Positions.
2. Place the air temperature switch of the front HVAC control module from the coldest to the warmest position.

Does the scan tool indicate that the value of the Rear Temp Dr. Actual parameter changes from the minimum specified value to the maximum specified value?

0-255 counts

Go to Step 9

Go to Step 14

9 | Inspect the air temperature sensor for the following conditions.

• | An obstruction to the airflow

• | A damaged or a missing seal to the sensor

• | Misaligned air ducts

• | A misaligned sensor

Did you find and correct the condition?

--

Go to Step 18

Go to Step 10

10 |

1. Install a thermometer near the air temperature sensor.
2. With a scan tool, observe the Duct Temp data parameters in the HVAC Module Sensors Data list.

Does the scan tool indicate that the sensor temperatures are within the specification at the thermometer temperatures?

-3 to +3°C (-5 to +5°F)

Go to Step 18

Go to Step 10

11 | Test the temperature sensor resistance. Refer to Sensor Resistance Table Does the resistance measure near the Sensor Resistance Table value? | -- | Go to Step 15 | Go to Step 13
12 | 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 . Did you find and correct the condition? | -- | Go to Step 18 | Go to Step 16
13 | Inspect for poor connections at the harness connector of the upper duct temp sensor, and lower duct temp sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 18 | Go to Step 15
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 . Did you find and correct the condition? | -- | Go to Step 18 | Go to Step 17
15 | Replace upper duct temp sensor or lower duct temp sensor. Refer to Duct Air Temperature Sensor Replacement - Upper , or Duct Air Temperature Sensor Replacement - Lower Did you complete the replacement? | -- | Go to Step 18 | --
16 | Replace the auxiliary HVAC control module. Refer to Auxiliary Heater and Air Conditioning Control Replacement for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 18 | --
17 | Replace the HVAC control module. Refer to Heater and Air Conditioning Control Replacement for replacement, setup, and programming. 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