GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The ambient air temperature sensor allows the HVAC control module to monitor the temperature of the air surrounding the front of the vehicle. The module applies 5 volts to internal input resistor that is connected to the signal circuit of the air temperature sensor. The module provides ground to the air temperature sensor through the low reference circuit. The HVAC control module monitors the voltage drop across the air temperature sensor and uses the input for automatic control calculations. When the air temperature is cold, the resistance of the sensor is high and the voltage signal is high. When the air temperature is hot, the resistances of the sensor is low and the voltage signal is low. The HVAC control module also uses the ambient air temperature input to calculate the value of the ambient air temperature display.

Conditions for Running the DTC

    • Battery voltage to the HVAC control module is greater than 8.7 V and less than 16.5 V.
    • The ignition is turned ON.

Conditions for Setting the DTC

The HVAC control module determines that the voltage applied to the input for the air temperature sensor is less than 0.09 V or greater than 4.9 V.

Action Taken When the DTC Sets

The HVAC control module uses a default value of 10°C (50°F) for the ambient air temperature display. The scan tool also displays 10°C (50°F) as the value for the Outside Air Temp. Raw parameter. This value will be displayed on the scan tool.

Conditions for Clearing the DTC

    • The DTC will become history if the HVAC control module no longer detects the condition that set the DTC.
    • The history DTC will clear after 100 fault free ignition cycles.
    • The DTC can be cleared with a scan tool.

Test Description

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

  1. Verifies that the condition that set the DTC is present.

Step

Action

Value(s)

Yes

No

Schematic Reference: HVAC Schematics

Connector End View Reference: HVAC Connector End Views

1

Did you perform the HVAC Diagnostic System Check?

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Go to Step 2

Go to Diagnostic System Check - HVAC Systems - Automatic

2

  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. Select the Heating and Air Conditioning display DTC function on the scan tool.

Does the scan tool indicate that B0159 is a current DTC?

--

Go to Step 3

Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

3

  1. Turn OFF the ignition.
  2. Disconnect the ambient air temperature sensor.
  3. Turn ON the ignition, with the engine OFF.
  4. Measure the voltage from the signal circuit of the ambient air temperature sensor to a good ground.

Does the voltage measure near the specified value?

5 V

Go to Step 4

Go to Step 5

4

Measure the voltage from the signal circuit to the low reference circuit of the ambient air temperature sensor.

Does the voltage measure near the specified value?

5 V

Go to Step 7

Go to Step 6

5

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

Did you find and correct the condition?

--

Go to Step 11

Go to Step 8

6

Test the low reference circuit of the ambient air temperature sensor for a high resistance or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 11

Go to Step 8

7

Inspect for poor connections at the harness connector of the ambient 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 11

Go to Step 9

8

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 11

Go to Step 10

9

Replace the ambient air temperature sensor. Refer to the Ambient Air Temperature Sensor Replacement .

Did you complete the replacement?

--

Go to Step 11

--

10

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

Did you complete the replacement?

--

Go to Step 11

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11

  1. Use the scan tool in order to clear the DTCs.
  2. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC reset?

--

Go to Step 2

System OK