Circuit Description
The HVAC control module monitors air temperature through air temperature sensors. When the air is cold, the sensor resistance and signal voltage are high. When the air is warm, the sensor resistance and signal voltage are low. The HVAC control module requests A/C compressor clutch engagement and controls the appropriate air temperature actuator door positions in order to maintain the selected air temperature on the HVAC control module. Output Air Temperature Sensor 2 circuit refers to the heater lower duct air temperature sensor.
DTC Descriptor
The diagnostic procedure supports the following DTC.
DTC B0179 Output Air Temperature Sensor 2 circuit
This vehicle has DTCs which include DTC Symptoms. For more information on DTC Symptoms, refer to DTC Symptom Description in Vehicle DTC Information.
The HVAC control module monitors the signal circuit of the lower air temperature sensor for the following conditions:
DTC Symptom | DTC Symptom Descriptor |
|---|---|
05 | Short to Battery or Open |
06 | Short to Ground or Open |
Conditions for Running
The ignition is turned ON.
Conditions for Setting the DTC
B0179 05 and 06
The HVAC control module detects the signal circuit is less than 5 counts (0.09 V) or greater than 250 counts (4.90 V).
Action Taken When the DTC Sets
B0179 05 and 06
A default value will be used for the sensor data by the HVAC control module.
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. |
| • | The DTC can be cleared with a scan tool. |
Diagnostic Aids
If the 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.
-
Tests for the proper operation of the circuit in the high voltage range.
-
Tests for the proper operation of the circuit in the low voltage range. If the fuse in the jumper opens when you perform this test, the signal circuit is shorted to voltage.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: HVAC Schematics Connector End View Reference: HVAC Connector End Views | ||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information |
2 |
Does the scan tool indicate that the sensor parameter is within the specified range? | 5-250 counts (0.09-4.90 V) | Go to Diagnostic Aids | Go to Step 3 |
Does the scan tool indicate that the sensor parameter is greater than the specified value? | 250 counts (4.90 V) | Go to Step 4 | Go to Step 5 | |
Does the scan tool indicate that the sensor parameter is less than the specified value? | 5 counts (0.09 V) | Go to Step 8 | Go to Step 6 | |
5 | Test the signal circuit of the lower duct air temperature sensor for a short to ground. 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 | Test the signal circuit of the lower duct air temperature sensor for a short to voltage, 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 7 |
7 | Test the low reference circuit of the lower duct 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 |
8 | Inspect for poor connections at the harness connector of the lower duct 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 10 |
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 lower duct air temperature sensor. Refer to 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 after module replacement. Refer to Actuator Recalibration . 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 |
