GM Service Manual Online
For 1990-2009 cars only

Object Number: 598757  Size: MF
HVAC Components
Air Temperature Sensors
Air Temperature Sensors
Handling Electrostatic Discharge Sensitive Parts Notice

Circuit Description

The heater-A/C control determines the outside air temperature through an input from the ambient air temperature sensor. The heater-A/C control receives a voltage signal from the ambient air temperature sensor through circuit 735 (LT GRN/BLK). The ambient air temperature sensor is grounded by the heater-A/C control through circuit 61 (YEL).

The internal resistance of the ambient air temperature sensor decreases as the temperature increases. The difference between the ambient air temperature sensor and the inside air temperature sensor measurements is used by the heater-A/C control in order to determine whether the incoming air should be cooled or warmed, and to what degree, in order to bring the inside air temperature to the selected temperature as quickly as possible. This is accomplished through operation of the control solenoids. The heater-A/C control also uses the signal from the ambient air temperature sensor in order to display the outside air temperature on the heater-A/C control display.

Conditions for Setting the DTC

The heater-A/C control performs a check on the operation of the ambient air temperature sensor and detects an open in circuit 735 (LT GRN/BLK).

Action Taken When the DTC Sets

    • The heater-A/C control stores DTC B0333 in memory.
    • The heater-A/C control uses 9°C (49°F) as a substitute for the ambient air temperature reading , allowing the A/C system to continue operation.

Conditions for Clearing the DTC

    • An open in circuit 735 (LT GRN/BLK) is no longer present.
    • Under all fault conditions, the ignition switch must be cycled from on to off, back to on before this DTC can change from current to history.
    • A history DTC clears after 100 drive cycles if a short to ground in circuit 735 (LT GRN/BLK) is no longer present.
    • Using a scan tool

Diagnostic Aids

The following conditions may cause this DTC to set:

    • A poor connection or open in circuit 735 (LT GRN/BLK)
    • A poor connection or open in circuit 61(YEL)
    • A faulty ambient air temperature sensor
    • A faulty heater-A/C control

Test Description

The number(s) below refer to the step number(s) on the diagnostic table.

  1. This step checks for proper voltage value at the ambient air temperature sensor.

  2. This step determines whether circuit 61 (YEL) or circuit 735 (LT GRN/BLK) is open.

  3. This step checks for an open in circuit 61 (YEL) .

  4. This step checks for an open in circuit 735 (LT GRN/BLK).

Step

Action

Value(s)

Yes

No

1

Was the heater-A/C control diagnostic system check performed?

--

Go to Step 2

Go to Diagnostic System Check

2

  1. Turn the ignition switch off.
  2. Disconnect the ambient air temperature sensor electrical connector.
  3. Turn the ignition switch on.
  4. Use a digital multimeter (DMM) to measure the voltage between the ambient air temperature sensor harness connector terminal A and terminal B.

Is the measured voltage within the specified range?

4.5-5.5V

Go to Step 6

Go to Step 3

3

Use a DMM to measure the voltage between the ambient air temperature sensor harness connector terminal A and ground.

Is the measured voltage within the specified range?

4.5-5.5V

Go to Step 4

Go to Step 5

4

  1. Turn the ignition switch off.
  2. Disconnect the heater-A/C control electrical connector.
  3. Use a DMM to measure the resistance between the heater-A/C control harness connector terminal D1 and the ambient air temperature sensor harness connector terminal B.

Is the measured resistance less than the specified value?

2ohms

Go to Step 8

Go to Step 7

5

  1. Turn the ignition switch off.
  2. Disconnect the heater-A/C control electrical connector.
  3. Use a DMM to measure the resistance between the heater-A/C control harness connector terminal D3 and the ambient air temperature sensor harness connector terminal A.

Is the measured resistance less than the specified value?

2ohms

Go to Step 8

Go to Step 9

6

  1. Check the ambient air temperature sensor connector terminals for poor contact and repair as needed. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.
  2. Replace the ambient air temperature sensor if the connector is OK. Refer to Ambient Temperature Sensor Replacement .

Is the repair complete?

--

Go to Step 10

--

7

Locate and repair a poor connection or an open in circuit 61(YEL). Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Is the repair complete?

--

Go to Step 10

--

8

  1. Check the heater-A/C control connector terminals for poor contact and repair as needed. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.
  2. Replace the heater-A/C control if the connector is OK . Refer to Control Assembly Replacement .

Is the repair complete?

--

Go to Step 10

--

9

Locate and repair a poor connection or an open in circuit 735 (LT GRN/BLK). Refer to Testing for Intermittent Conditions and Poor Connections and Circuit Testing in Wiring Systems.

Is the repair complete?

--

Go to Step 10

--

10

Verify proper operation of the system.

Does the system operate properly?

--

System OK

Go to Diagnostic System Check