Circuit Description
The following DTCs are for the ambient air temperature sensor and for the inside air temperature sensor assembly:
| • | B0159 is for the ambient air temperature sensor. |
| • | B0164 is for the inside air temperature sensor assembly. |
The ambient air temperature sensor allows the HVAC control module to monitor the temperature of the air surrounding the front of the vehicle. The inside air temperature sensor assembly allows the HVAC control module to monitor the temperature of the air inside the passenger compartment. The module applies 5 volts to internal input resistors that are connected to the signal circuits of the air temperature sensors. The module provides ground to the air temperature sensors through the low reference circuits. The HVAC control module monitors the voltage drops across the air temperature sensors and uses the inputs for automatic control calculations. The HVAC control module also uses the ambient air temperature input to calculate the value of the ambient air temperature display. When the air temperatures are cold, the resistances of the sensors are high and the voltage signals are high. When the air temperatures are hot, the resistances of the sensors are low and the voltage signals are low.
Conditions for Running the DTC
| • | Battery voltage to the HVAC control module is greater than 8.7 V and less than 16.5 V. |
| • | The ignition is turned ON. |
Conditions for Setting the DTC
The HVAC control module determines that the voltage applied to the input for the air temperature sensor is less than 0.09 V or greater than 4.9 V.
Action Taken When the DTC Sets
| • | The HVAC control module uses a default value of 10°C (50°F) for the ambient air temperature display. The scan tool also displays 10°C (50°F) as the value for the Outside Air Temp. Raw parameter. |
| • | The HVAC control module use a default value of 25°C (77°F) for the Inside Air Temp. parameter. |
Conditions for Clearing the DTC
| • | The DTC will become history if the HVAC control module no longer detects the condition that set the DTC. |
| • | The history DTC will clear after 100 fault free ignition cycles. |
| • | The DTC can be cleared with a scan tool. |
Test Description
The number below refers to the step number on the diagnostic table.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Schematic Reference: HVAC Schematics Connector End View Reference: HVAC Connector End Views | ||||
1 | Did you perform the HVAC Diagnostic System Check? | -- | Go to Step 2 | |
Does the scan tool indicate that B0159 or B0164 is a current DTC? | -- | Go to Step 3 | Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems | |
3 |
Does the voltage measure near the specified value? | 5 V | Go to Step 4 | Go to Step 5 |
4 | Measure the voltage from the signal circuit to the low reference circuit of the appropriate air temperature sensor. Does the voltage measure near the specified value? | 5 V | Go to Step 7 | Go to Step 6 |
5 | Test the signal circuit of the appropriate air temperature sensor for an open, high resistance, short to ground, or short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 11 | Go to Step 8 |
6 | Test the low reference circuit of the appropriate air temperature sensor for a high resistance or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 11 | Go to Step 8 |
7 | Inspect for poor connections at the harness connector of the appropriate air temperature sensor assembly. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 11 | Go to Step 9 |
8 | Inspect for poor connections at the harness connector of the HVAC control module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 11 | Go to Step 10 |
9 | Replace the air temperature sensor assembly. Refer to the appropriate replacement procedure: Did you complete the replacement? | -- | Go to Step 11 | -- |
10 | Replace the HVAC control module. Refer to HVAC Control Module Replacement . Did you complete the replacement? | -- | Go to Step 11 | -- |
11 |
Does the DTC reset? | -- | Go to Step 2 | System OK |
