Instrument Panel, Gauges and Warning Indicators Diagnosis

DTC B0158

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

IMPORTANT: Always perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Testing and Inspection

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 provides ground through the low reference circuit. 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 battery displays +189.5°F (+87.5°C).

CONDITIONS FOR RUNNING THE DTC
The ignition is in ACCESSORY or RUN
- The ignition is ON.
- The system voltage is between 9-16 volts.

CONDITIONS FOR SETTING THE DTC
- The HVAC module detects that the outside air temperature is -40°F (-40°C).
- The HVAC module detects that the outside air temperature is +189.5°F (+87.5°C).

ACTION TAKEN WHEN THE DTC SETS
- "SC" is displayed in the DIC when the OAT sensor resistance value is less than the lowest OAT sensor resistance threshold.
- "OC" is displayed in the DIC when the OAT sensor resistance value is greater than the highest OAT sensor resistance threshold.

CONDITIONS FOR CLEARING THE DTC
- The DTC becomes history when the conditions for setting the DTC are no longer present.
- The history DTC clears after 40 malfunction-free warm-up cycles.
- The HVAC module receives a clear code command from the scan tool.

CIRCUIT/SYSTEM TESTING
1. With the ignition OFF disconnect the OAT sensor.
2. Turn ON the ignition with the engine OFF.
- If the DIC does not display "OC", test the OAT sensor signal circuit for a short to ground, an open or high resistance.
- If the OAT sensor signal circuit tests normal, replace the HVAC module.
3. With the ignition OFF, connect a 3-amp fused jumper wire between the signal circuit of the OAT sensor and a good ground.
4. Turn ON the ignition.
- If the DIC displays "SC", test the OAT sensor ground circuit for an open or a high resistance.
- If the OAT sensor ground circuit tests normal, replace the OAT sensor.
- If the DIC does not displays "SC", test the OAT sensor signal circuit for an open, a short to voltage or a high resistance.
- If the OAT sensor signal circuit tests normal, replace the HVAC module.

REPAIR INSTRUCTIONS

IMPORTANT: Always perform the Diagnostic Repair Verification after completing the diagnostic procedure.
- Ambient Air Temperature Sensor Replacement
- Control Module References for the HVAC module replacement, setup and programming