GM Service Manual Online
For 1990-2009 cars only

Test Description

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

  1. If the vehicle has not been driven for at least 90 minutes you do not need to drive vehicle to update the outside air temperature display.

Step

Action

Yes

No

Schematic Reference : HVAC Schematics

DEFINITION: The ambient air temperature display is inaccurate, and no DTC are set.

1

Did you perform the HVAC Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check - HVAC Systems - Automatic

2

  1. Start the engine.
  2. Observe the Outside Air Temp. parameter in the Primary ECC Data list.
  3. Drive the vehicle faster than 8 km/h (5 mph) in order to update the module.
  4. Measure the ambient air temperature.

Is the Outside Air Temp. parameter within 3°C (5°F) of the ambient air temperature?

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

Go to Step 3

3

  1. Turn OFF the ignition.
  2. Disconnect the ambient air temperature sensor.
  3. Measure the resistance of the ambient air temperature sensor. Refer to Sensor Resistance Table .
  4. Compare the measured resistance to the value in the Sensor Resistance Table.

Does the resistance measure near the specified value?

Go to Step 4

Go to Step 6

4

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

Did you find and correct the condition?

Go to Step 10

Go to Step 5

5

Test the low reference circuit for a short to ground, for a high resistance, or for an open. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 10

Go to Step 7

6

Inspect for poor connections at the harness connector of the ambient air temperature sensor. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 10

Go to Step 8

7

Inspect for poor connections at the harness connector of the HVAC control module. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 10

Go to Step 9

8

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

Did you complete the replacement?

Go to Step 10

--

9

Important: Perform the calibration 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 10

--

10

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 3