Diagnostic Instructions

DTC Descriptors

DTC B0158 03: Outside Air Temperature (OAT) Sensor Circuit Voltage Below Threshold

DTC B0158 07: Outside Air Temperature (OAT) Sensor Circuit Voltage Above Threshold

Diagnostic Fault Information

Circuit	Short to Ground	Open/High Resistance	Short to Voltage
Outside Air Temperature (OAT) Signal Circuit	B0158 1	B0158 1	B0158 1
Outside Air Temperature (OAT) Ground Reference Circuit	1	B0158 1	1
1. Outside Air Temperature (OAT) Display Inaccurate or Inoperative

Circuit/System Description

The HVAC module monitors the signal circuit of the outside air temperature sensor. The outside air temperature (OAT) sensor is a thermistor which varies in resistance as the temperature changes. When the resistance of OAT sensor increases, the outside air temperature is cold. When the resistance of the OAT sensor decreases, the outside air temperature is high. The HVAC module interfaces with the ambient air temperature via two discreet circuits. The HVAC module applies 5 volts to an internal input resistor that is connected to the signal circuit of the outside air temperature sensor. The HVAC module uses the outside air temperature resistance and voltage for automatic control calculations and conversion to temperature values. The HVAC module sends the temperature value to the instrument panel cluster (IPC) via GMLAN serial data circuits for display in the driver information center (DIC). If the OAT sensor is opened or shorted, the temperature display is either a cold or hot extreme. An open OAT sensor will display -40°F (-40°C) in the DIC and an OAT sensor shorted to ground displays +189.5°F (+87.5°C).

Conditions for Running the DTC

The ignition is in ACCESSORY or RUN

Conditions for Setting the DTC

Action Taken When the DTC Sets

Conditions for Clearing the DTC

Reference Information

Schematic Reference

Connector End View Reference

Description and Operation

Air Temperature Description and Operation

Electrical Information Reference

Scan Tool Reference

Circuit/System Verification

The DIC should display approximately 189.5°F (+87.5°C) or -40°F (-40°C) .

Circuit/System Testing

1. Ignition OFF disconnect the OAT sensor connector.
2. Ignition OFF, test for less than 1 ohm of resistance between the ground circuit terminal and ground.

⇒	If greater than 1 ohm, test the ground circuit for an open/high resistance.

3. Ignition ON, verify the driver information center (DIC) displays approximately -40°F (-40°C).

⇒	If the DIC does not display approximately -40°F (-40°C), test the OAT sensor signal circuit for a short to ground. If the circuit tests normal, replace the HVAC module.

4. Ignition ON, perform an outside air temperature Instant Update to by pass filtering by simultaneously pressing the following switches on the HVAC control module:

•

AUTO

•

A/C OFF

•	REAR DEFOGGER

5. Ignition ON, install a 3-amp fused jumper wire between the signal circuit and the ground circuit of the OAT sensor. Verify the DIC displays approximately 189.5°F (+87.5°C).

⇒	If the DIC does not displays approximately 189.5°F (+87.5°C), test the signal circuit of the OAT sensor for a short to voltage or an open/high resistance. If the circuit tests normal, replace the HVAC module.

6. If all circuits test normal, test or replace the OAT sensor.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.