For 1990-2009 cars

### Diagnostic Instructions

• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

• | Strategy Based Diagnosis

• | Diagnostic Procedure Instructions

### DTC Descriptor

DTC B0158 13: Outside Air Temperature Sensor Voltage Low.
DTC B0158 14: Outside Air Temperature Sensor Voltage High.

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Ambient Air Temperature Sensor Signal Circuit | B0158 14 | B0158 14 B0158 13 | B0158 13 | --
Low Reference Circuit | -- | B0158 14 B0158 13 | -- | --

### Circuit/System Description

The HVAC Control Module monitors the ambient air temperature sensor to display ambient air temperature. The temperature sensor is a 2-wire negative temperature co-efficient thermistor. The HVAC Control Module applies 5 volts to an internal input resistor that is connected to the signal circuits of the ambient air temperature sensor. The HVAC Control Module provides the ground to the ambient air temperature sensor through the low reference circuit. The HVAC Control Module monitors the voltage drop across the ambient air temperature sensor and uses the input for automatic control calculations. When the ambient air temperatures are cold, the resistance of the sensor is high and the voltage signals are high. When the ambient air temperatures are hot; the resistance of the sensors is low and the voltage signals are low. The HVAC Control Module converts the voltage value to a temperature value of Celsius and Farenhiet that will be displayed by the driver information center (DIC).

### Conditions for Running the DTC

The ignition is turned ON.

### Conditions for Setting the DTC

• | The HVAC control module detects the sensor signal circuit is less than 4.8 volt.

• | The HVAC control module detects the sensor signal circuit is more than 5.2 volts.

### Action Taken When the DTC Sets

• | The default value of 29°C (85°F) will be substituted for the ambient air temperature sensor data by the HVAC contol module.

• | The driver information center (DIC) will display the set temperature when ON.

### Conditions for Clearing the DTC

• | The DTC will become history if the HVAC control module no longer detects a failure.

• | The history DTC will clear after 40 fault-free ignition cycles.

### Reference Information

#### Schematic Reference

• | HVAC Schematics

• | Driver Information System Schematics

#### Connector End View Reference

• | HVAC Connector End Views

• | Displays and Gages Connector End Views

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

#### Scan Tool Reference

• | Scan Tool Data List

• | Scan Tool Data Definitions

• | Scan Tool Output Controls

### Circuit/System Verification

Ignition ON, Engine OFF, observe the Ambient Air Temperature Sensor temperature through the Driver Information Center (DIC). The reading should be the ambient temperature setting. If the display of the DIC for temperature reads dashes, check for a sensor signal circuit fault.

### Circuit/System Testing

1. Ignition OFF, disconnect the ambient air temp sensor harness connector at the ambient air temp sensor terminal A.
2. Test for less than 1.0 ohm of resistance between the low reference circuit terminal B and ground.

⇒ | If greater than the specified value, test the low reference circuit for an open / high resistance.. If the circuit tests normal, replace the HVAC control module.

3. Ignition ON, test for 5 volts between the low reference circuit terminal B and the 5-volt reference signal terminal A.

⇒ | If not the specified voltage, test the signal circuit for a short to voltage, short to ground or open/high resistance. If the circuit tests normal, replace the HVAC control module.

4. If all circuits test normal, replace the ambient air temperature sensor.

### Repair Instructions

Important: Always perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Ambient Air Temperature Sensor Replacement

• | Control Module References for HVAC control module +replacement, setup, and programming