Circuit Description
The HVAC control module monitors the air temperature in the upper center A/C discharge duct via an upper air temperature sensor. 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.
Conditions for Running the DTC
The ignition is turned ON.
Conditions for Setting the DTC
The HVAC control module detects the signal circuit is less than 0.09 V (5 counts) or greater than 4.90 V (250 counts).
Action Taken When the DTC Sets
A default value will be used for the sensor data by the HVAC control module. The sensor reading displayed on the scan tool in the HVAC data list will be this default value.
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 50 fault free ignition cycles. |
| • | The DTC can be cleared with a scan tool. |
Diagnostic Aids
If condition 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 | ||||
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 upper air temperature sensor signal circuit to the low reference circuit of the upper air temperature sensor. Does the voltage measure near the specified value? | 5 V | Go to Step 6 | Go to Step 5 |
4 | Test the upper air temperature sensor signal circuit 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 upper 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 upper 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 upper 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 upper air temperature sensor. Refer to Air Temperature Sensor Replacement - Upper . 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 |
