Circuit Description
The following DTCs are for the upper air temperature sensor and for the lower air temperature sensor :
| • | B0175 and B0176 are for the upper air temperature sensor. |
| • | B0180 and B0181 are for the lower air temperature sensor. |
Air temperature sensors allow the HVAC control module to monitor the temperature of the discharge air in the HVAC ducts. 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 circuit. The HVAC control module monitors the voltage drops across the air temperature sensors and uses the inputs for automatic control calculations. When the duct air temperatures are cold, the resistances of the sensors are high and the voltage signals are high. When the duct air temperatures are hot, the resistances of the sensors are low and the voltage signals are low.
Conditions for Running the DTC
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, for B0175 and B0180, or greater than 4.9 V, for B0176 and B0181.
Action Taken When the DTC Sets
The HVAC control module uses a default temperature sensor value until the fault is cleared. This default value will be displayed on the scan tool.
Conditions for Clearing the DTC
| • | The DTC becomes history when the HVAC control module no longer detects a failure. |
| • | The history DTC clears after 50 fault free ignition cycles. |
| • | The DTC can be cleared with a scan tool. |
Diagnostic Aids
| • | Visually inspect the sensor connector and harness for corrosion and damage. The resistance value of the sensor must be between 47-101,000 ohms. If the resistance is not within the specified value, replace the sensor. |
| • | Insure upper and lower air temperature sensor is in place and secure. Insure no restrictions or debris around the air temperature sensor this will give incorrect reading to HVAC control module. |
| • | If condition is not present, refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
Scan tool uses a default value, this will not give accurate reading of sensor value if open or short to ground.
-
Tests for the possibility of a short to another 5 V reference circuit.
Step | Action | Values | 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 voltage measure near the specified value? | 5 V | Go to Step 3 | Go to Step 4 | |
3 | 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 6 | Go to Step 5 |
4 | 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 12 | Go to Step 9 |
5 | 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 12 | Go to Step 9 |
6 | Inspect for poor connections at the harness connector of the appropriate air temperature sensor. 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 12 | Go to Step 7 |
7 | Test the appropriate air temperature sensor resistance. Refer to the Sensor Resistance Table . Does the resistance measure near the Sensor Resistance Table value? | -- | Go to Step 8 | Go to Step 10 |
Did you find and correct the condition? | -- | Go to Step 12 | Go to Step 9 | |
9 | 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 12 | Go to Step 11 |
10 | Replace the appropriate air temperature sensor. Refer to Air Temperature Sensor Replacement - Upper or Air Temperature Sensor Replacement - Lower . Did you complete the replacement? | -- | Go to Step 12 | -- |
11 |
Important:: Perform the recalibration procedure for the HVAC control module. Replace the HVAC control module. Refer to HVAC Control Module Replacement . Did you complete the replacement? | -- | Go to Step 12 | -- |
12 |
Does the DTC reset? | -- | Go to Step 2 | System OK |
