GM Service Manual Online
For 1990-2009 cars only

Conditions for Setting the DTC

This code will set if the output of the ambient air temperature sensor indicates a probable short circuit or an open in the sensor or the associated wiring harness, or a malfunction of the full automatic temperature control (FATC) controller.

Step

Action

Values

Yes

No

1

  1. Turn OFF the ignition.
  2. Disconnect the ambient air temperature sensor connector from the front bumper harness located behind the front bumper.
  3. Measure the resistance between the ambient air temperature sensor connector terminals.

Is there any sign of damage in the wiring or connector, or the resistance outside of the specified value at 20-25°C (68-70°F)?

2600-2100 ohms

Go to Step 5

Go to Step 2

2

  1. Remove the ambient air temperature sensor.
  2. Examine the wiring for any open or short and the connector for any damage.

Is there a problem with the wiring or the connector?

--

Go to Step 3

Go to Step 4

3

Repair the problem found in the ambient air temperature sensor wiring or connector.

Did you complete the repair?

--

System OK

--

4

Replace the ambient air temperature sensor.

Did you complete the repair?

--

System OK

--

5

  1. Turn ON the ignition.
  2. Measure the voltage between the 2 terminals in the ambient air temperature sensor connector on the front bumper.

Does the voltage measure greater than the specified value.

4 V

Go to Step 7

Go to Step 6

6

  1. Reconnect the ambient air temperature sensor to the connector.
  2. Turn ON the ignition.
  3. Observe the temperature display screen on the controller.

Does the display indicate the continuing presence of a DTC 2 condition?

0 V

Go to Step 8

System OK

7

  1. Pull the full automatic temperature control (FATC) controller from the instrument panel, leaving the wiring harness connected.
  2. Measure the voltage between terminals B13 and A4 by back probing the connectors.

Does the voltage measure equal to the specified value?

4 V

Go to Step 8

Go to Step 9

8

Replace the FATC controller.

Did you complete the repair?

--

System OK

--

9

  1. Trace the wiring for ambient air temperature sensor from FATC controller to ambient air temperature sensor connector.
  2. Repair any open or high resistance condition in the wiring or connector terminal.

Did you complete the repair?

--

System OK

--