B0158

DTC B0158

DTC DESCRIPTOR

DTC B0158
Ambient Air Temperature Sensor Circuit

DIAGNOSTIC FAULT INFORMATION






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

CIRCUIT/SYSTEM DESCRIPTION
The body control module (BCM) monitors the ambient air temperature sensor to display ambient air temperature. The temperature sensor is a 2-wire negative temperature co-efficient thermistor. The BCM applies 5 volts to an internal input resistor that is connected to the signal circuits of the ambient air temperature sensor. The BCM provides the ground to the ambient air temperature sensor through the low reference circuit. The BCM 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 BCM converts the voltage value to a temperature value of Celsius and Fahrenheit that will be displayed by the instrument cluster display (IPC).

CONDITIONS FOR RUNNING THE DTC
The ignition is turned ON.

CONDITIONS FOR SETTING THE DTC
- The BCM detects the sensor signal circuit is less than 0.1 volt.
- The BCM detects the sensor signal circuit is more than 4.9 volts.

ACTION TAKEN WHEN THE DTC SETS
- The default value of 3°C (38°F) will be substituted for the ambient air temperature sensor data by the BCM.
- The instrument cluster display (IPC) will display the set temperature when ON.

CONDITIONS FOR CLEARING THE DTC
- The DTC will become history if the BCM no longer detects a failure.
- The history DTC will clear after 40 fault-free ignition cycles.
- Using a scan tool can clear the DTC.

CIRCUIT/SYSTEM VERIFICATION
The ambient air temperature sensor must cool down prior to checking normal operation for the temperature display reading to be believable. With the Ignition ON, check the Ambient Air Temperature Sensor readout on the IPC. The temperature readout should be in the range of normal outside temperature.

With the ignition OFF, disconnect the ambient air temperature sensor, Turn ON the ignition with the engine OFF, observe the Ambient Air Temperature Sensor Signal Circuit parameter in the BCM data list.

In the following tests if the fuse in the jumper opens when you perform this test, the signal circuit is shorted to voltage.
1. If more than 4.9 volts, connect a 3-amp fused jumper between the sensor signal circuit and the low reference circuit. With IGN ON and engine OFF, observe the Ambient Air Temperature parameter in the scan tool BCM data list. If the voltage reading is less than 0.1 volt, and circuit/connections test normal, replace the ambient air temperature sensor.
2. If more than 4.9 volts, connect a 3-amp fused jumper between the sensor signal circuit and the low reference circuit. With IGN ON and engine OFF, observe the Ambient Air Temperature parameter in the scan tool BCM data list. If the voltage reading is more than 0.1 volt, test the signal circuit for a short to voltage, high resistance or an open. If the circuit/connections test normal, test the low reference circuit for an open or high resistance. If the circuit/connections test normal replace the BCM.
3. If less than 4.9 volts, test the ambient air temperature sensor signal circuit for a short to ground. If the circuit/connections test normal replace the BCM.

REPAIR INSTRUCTIONS

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