Circuit Description
The HVAC control module monitors the ambient air temperature via an ambient air temperature sensor. When the air is cold, the sensor resistance and the signal voltage are high. When the air is warm, the sensor resistance and the signal voltage are low. The HVAC control module displays the outside air temperature.
Conditions for Running the DTC
The ignition is turned ON.
Conditions for Setting the DTC
The HVAC control module detects the fault when the signal circuit is more than 4.9 volts.
Action Taken When the DTC Sets
The HVAC control module uses a default temperature sensor value until the fault is cleared.
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 ambient air temperature sensor shield is in place. If this is not in place it could lead to excessive air flow across sensor and 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.
-
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 | Value(s) | Yes | No |
|---|---|---|---|---|
Schematic Reference: HVAC Schematics | ||||
1 | Did you perform the HVAC Diagnostic System Check? | -- | Go to Step 2 | |
2 |
Does the scan tool indicate that the Outside Air Temp parameter is within the specified range? | -40 to +80°C (-40 to +176°F) | Go to Diagnostic Aids | Go to Step 3 |
Does the scan tool indicate that the Outside Air Temp parameter is greater than the specified value? | -53°C (-65°F) | Go to Step 4 | Go to Step 5 | |
Does the scan tool indicate that the Outside Air Temp parameter is greater than the specified value? | 125°C (257°F) | Go to Step 8 | Go to Step 6 | |
5 | Test the signal circuit of the ambient 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 ambient 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 ambient 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 outside 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 ambient air temperature sensor. Refer to Ambient Air Temperature Sensor Replacement . 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 |
