Diagnostic Instructions

DTC Descriptors

DTC B0158 04: Outside Air Temperature (OAT) Sensor Open

DTC B0158 05: Outside Air Temperature (OAT) Sensor Short to Battery or Open

DTC B0158 06: Outside Air Temperature (OAT) Sensor Short to Ground or Open

Diagnostic Fault Information

Circuit	Short to Ground	Open/High Resistance	Short to Voltage
Outside Air Temperature (OAT) Signal Circuit	B0158 06	B0158 04	B0158 05
Outside Air Temperature (OAT) Ground Reference Circuit	--	B0158 04	--

Circuit/System Description

The HVAC module monitors the signal circuit of the ambient air temperature sensor. The ambient air temperature sensor is a thermistor which varies in resistance as the temperature changes. When the resistance of the ambient air temperature sensor increases, the ambient air temperature is cold. When the resistance of the ambient air temperature sensor decreases, the ambient air temperature is high. The HVAC module interfaces with the ambient air temperature sensor via 2 discreet circuits. The HVAC module applies 5 volts to an internal input resistor that is connected to the signal circuit of the ambient air temperature sensor . The HVAC module provides ground through the low reference circuit. The HVAC module uses the ambient air temperature sensor resistance and voltage for automatic control calculations and conversion to temperature values. The HVAC module displays the ambient air temperature and if the ambient air temperature sensor is opened or shorted, the temperature display is either a cold or hot extreme. An open ambient air temperature sensor displays -40°F (-40°C) and an ambient air temperature sensor shorted to ground displays 189.5°F (87.5°C).

Conditions for Running the DTC

Conditions for Setting the DTC

Action Taken When the DTC Sets

Conditions for Clearing the DTC

Reference Information

Schematic Reference

Connector End View Reference

Electrical Information Reference

Scan Tool Reference

Circuit/System Verification

The HVAC module should display 189.5°F (87.5°C) or -40°F (-40°C) .

Circuit/System Testing

1. Ignition OFF disconnect the harness connector at the ambient air temperature sensor.
2. Ignition OFF, test for less than 1 ohm of resistance between the ambient air temperature sensor low reference circuit terminal B and ground.

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

3. Ignition ON, verify the HVAC module displays approximately -40°F (-40°C).

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

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

•	LEFT TEMPERATURE UP

•	PASS ENABLE

•	REAR DEFOG ENABLE

5. Ignition ON, install a 3-amp fused jumper wire between the ambient air temperature sensor signal circuit terminal A and the ambient air temperature low reference circuit terminal B. Verify the HVAC module displays approximately 189.5°F (87.5°C).

⇒	If the HVAC does not display approximately 189.5°F (87.5°C), test the ambient air temperature sensor signal circuit 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 ambient air temperature sensor.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.