GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Saturn 🢒 2008 🢒 VUE - FWD 🢒 HVAC 🢒 HVAC - Automatic 🢒 Air Temperature Malfunction

Diagnostic Instructions
    • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    • Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    •  Diagnostic Procedure Instructions provides an overview of each diagnostic category.

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Inside Air Temperature Sensor Aspirator Fan Control

1

1

--

--

Ambient Air Temperature Sensor Signal

B0158 13

B0158 13

B0158 14

1

Inside Air Temperature Sensor Signal

B0163 02

B0163 05

B0163 05

1

Upper Air Temperature Sensor Signal

B0173 02

B0173 05

B0173 05

1

Lower Air Temperature Sensor Signal

B0178 02

B0178 05

B0178 05

1

Left Sunload Sensor Signal

B0183 02

B0183 05

B0183 05

1

Right Sunload Sensor Signal

B0188 02

B0188 05

B0188 05

1

Evaporator Temperature Sensor Signal

B3933 14

B3933 13, B3933 14

B3933 13

1

Low Reference

--

B3933 05, B0158 05, B0163 05

--

--

Sunload Sensors Ground

--

B0183 05, B0188 05

--

--

Inside Air Temperature Sensor Aspirator Ground

--

1

--

--

1. Air Temperature Malfunction

Circuit/System Description

Air Temperature Sensors

The air temperature sensors are a 2-wire negative temperature co-efficient thermistor. The vehicle uses the following air temperature sensors:

    • Ambient air temperature sensor
    • Inside air temperature sensor assembly
    • Upper air temperature sensor
    • Lower air temperature sensor
    • A/C evaporator temperature sensor

A signal and low reference circuit enables the sensor to operate. As the air temperature surrounding the sensor increases, the sensor resistance decreases. The sensor signal voltage decreases as the resistance decreases. The sensor operates within a temperature range between -40 to +101°C (-40 to +215°F). The sensor signal varies between 0-5 volts. The input of the duct air temperature sensors are different from the ambient and inside air temperature sensors. The HVAC control module converts the signal to a range between 0-255 counts. As the air temperature increases the count value will decrease.

Sun Load Sensor Assembly

The sunload sensor is a 2-wire photo diode. The vehicle uses left and right sunload sensors. The 2 sensors are integrated into the sunload sensor assembly. Low reference and signal circuits enable the sensor to operate. As the light shining upon the sensor gets brighter, the sensor resistance increases. The sensor signal decreases as the resistance increases. The sensor operates within an intensity range between completely dark and bright. The sensor signal varies between 0-5 volts. The HVAC control module converts the signal to a range between 0-255 counts. The sunload sensor provides the HVAC control module a measurement of the amount of light shining on the vehicle. Bright, or high intensity, light causes the vehicles inside temperature to increase. The HVAC system compensates for the increased temperature by diverting additional cool air into the vehicle. If the HVAC control module detects a malfunctioning sensor, then the control module software will use a defaulted sunload value.

Diagnostic Aids

Condition

Display

Using Scan Tool Special Function

Updates temperature display instantly

When the HVAC module A/C and RECIRCULATION buttons are pressed simultaneously

Updates temperature display instantly

At start up with the engine off less than 2 hours

Displays last stored temperature unless temperature has decreased. The outside air temperature reading is always instantly updated if ambient air temperature has decreased.

At start up with the engine off more than 2 hours

Displays actual outside temperature

Vehicle speed above 32 km/h (20 mph) for a minimum of 80 seconds

Updates temperature display at a slow filtered rate

Vehicle speed above 72 km/h (45 mph)

Displays actual outside temperature

Sensor ambient temperature reading is less than the last displayed value

Displays actual outside temperature

When the ambient air decreases

Updates temperature display rapidly

Reference Information

Schematic Reference

HVAC Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

    •  Air Delivery Description and Operation
    •  Air Temperature Description and Operation

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification
  1. Ignition ON, cover the sunload sensor assembly with a shop towel or other suitable item. Verify the scan tool Right Sunload Sensor and Left Sunload Sensor parameters are within 3 counts of each other.
    2. ⇒If not within the specified range, refer to Sun Load Sensor Circuit Malfunction.
  2. Measure actual outside air temperature using a thermometer. Compare this value to the scan tool Outside Air Temp. Raw parameter. The measured temperature should be within 5 degrees of parameter.
    3. ⇒If not within the specified range, refer to Ambient Air Temperature Sensor Circuit Malfunction.
  3. Measure actual inside air temperature using a thermometer. Compare this value to the scan tool Inside Air Temp. Sensor parameter. The measured temperature should be within 5 degrees of parameter.
    4. ⇒If not within the specified range, refer to Inside Air Temperature Sensor Circuit Malfunction.
  4. Measure actual temperature using a thermometer at each of the duct temperature sensors. Compare this value to the appropriate scan tool Duct Actual parameter. The measured temperature should be within 5 degrees of appropriate Duct Actual parameter.
    5. ⇒If not within the specified range, refer to Duct Temperature Sensor Circuit Malfunction.

Circuit/System Testing

Sun Load Sensor Circuit Malfunction

  1. Ignition OFF, disconnect the harness connector at the sunload sensor.
  2. Test for less than 10 ohms between the ground circuit terminal C and ground.
    3. ⇒If greater than the specified range, test the ground circuit for an open/high resistance.
  3. Ignition ON, test for 4.8-5.2 volts between the ground circuit terminal C and the appropriate signal circuit terminal listed below:
    4. • Left solar load sensor circuit terminal A
    • Right solar load sensor circuit terminal B
    ⇒If less than the specified range, test the signal circuit for a short to ground or open/high resistance. If the circuit tests normal, replace the HVAC control module.
    ⇒If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the HVAC control module.
  4. If all circuits test normal, test or replace the sunload sensor.

Ambient Air Temperature Sensor Circuit Malfunction

  1. Ignition OFF, disconnect the harness connector at the ambient air temperature sensor.
  2. Ignition OFF, test for less than 10 ohms between the following low reference circuit terminal B and ground.
    3. ⇒If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the HVAC control module.
  3. Ignition ON, verify the scan tool Outside Air Temp. Raw parameter is less than -35°C (-39°F).
    4. ⇒If greater than the specified range, test the following signal circuit terminal A for a short to ground. If the circuit tests normal, replace the HVAC control module.
  4. Install a 3A fused jumper wire between the following signal circuit terminal A and the low reference circuit terminal B. Verify the scan tool Outside Air Temp. Raw parameter is greater than 85°C (185°F).
    5. ⇒If less than the specified range, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the HVAC control module.
  5. If all circuits test normal, test or replace the ambient air temperature sensor.

Inside Air Temperature Sensor Circuit Malfunction

  1. Ignition OFF, disconnect the harness connector at the inside air temperature sensor.
  2. Test for less than 1 ohm between the ground circuit terminal C and ground.
    3. ⇒If greater than the specified range, test the ground circuit for an open/high resistance.
  3. Ignition ON, verify a test lamp illuminates between the control circuit terminal B and ground.
    4. ⇒If the test lamp does not illuminate, test the ground circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the HVAC control module.
  4. Ignition OFF, test for less than 10 ohms between the low reference circuit terminal D and ground:
    5. ⇒If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the HVAC control module.
  5. Ignition ON, verify that the scan tool Inside Air Temp. Sensor parameter is less than -35°C (-39°F).
    6. ⇒If greater than the specified range, test the signal circuit terminal A for a short to ground. If the circuit tests normal, replace the HVAC control module.
  6. Install a 3A fused jumper wire between the signal circuit terminal A and the low reference circuit terminal D. Verify the scan tool Inside Air Temp. Sensor is greater than 98°C (208°F).
    7. ⇒If less than the specified range, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the HVAC control module.
  7. If all circuits test normal, test or replace the inside air temperature sensor.

Duct Temperature Sensor Circuit Malfunction

  1. Ignition OFF, disconnect the harness connector at the appropriate duct temperature sensor.
  2. Ignition OFF, test for less than 10 ohms between the low reference circuit terminal 2 listed below and ground:
    3. ⇒If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the HVAC control module.
  3. Ignition ON, verify that the appropriate scan tool Duct Actual parameter is less than -35°C (-39°F).
    4. ⇒If greater than the specified range, test the signal circuit terminal 1 for a short to ground. If the circuit tests normal, replace the HVAC control module.
  4. Install a 3A fused jumper wire between the signal circuit terminal 1 and the low reference circuit terminal 2. Verify the appropriate scan tool Duct Actual parameter is greater than 98°C (208°F).
    5. ⇒If less than the specified range, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the HVAC control module.
  5. If all circuits test normal, test or replace the appropriate duct temperature sensor.

Component Testing
  1. A thermometer can be used to test the sensor off the vehicle in warn and or cold water. Sensor Resistance Table for this test.
  2. Test the appropriate temperature sensor by varying the sensor temperature in water while monitoring the sensor resistance.
  3. Compare the readings with the Temperature VS Resistance table and verify that the resistance is within 5 percent of the specification.
    4. ⇒If not within the specified range, replace the sensor.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Duct Air Temperature Sensor Replacement - Upper
    •  Duct Air Temperature Sensor Replacement - Lower
    •  Inside Air Temperature Sensor Replacement
    •  Headlamp Automatic Control Ambient Light Sensor Replacement
    •  Control Module References for HVAC replacement, setup, and programming