Circuit Description
The heater and A/C control monitors the left heater duct via a LH air duct 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. The heater and A/C control requests A/C compressor clutch engagement and controls the air temperature actuator door positions in order to maintain the selected air temperature on the heater and A/C control.
Conditions for Running the DTC
The ignition is turned ON.
Conditions for Setting the DTC
LH air duct temperature sensor signal circuit (circuit 923) stays at or near 0 volts.
Action Taken When the DTC Sets
| • | The heater and A/C control stores a DTC 12 in memory. |
| • | The system will use a default value. |
Conditions for Clearing the DTC
| • | The DTC will become history if the heater and A/C control no longer detects a failure. |
| • | The history DTC will clear after 20 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 voltage.
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 circuit 923 to circuit 922 of the LH air duct temperature sensor. Does the voltage measure near the specified value? | 5 V | Go to Step 6 | Go to Step 5 |
4 | Test circuit 923 of the LH air duct 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 circuit 922 of the LH air duct 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 LH air duct temperature sensor. 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 LH air duct temperature sensor resistance. Does the resistance measure within the specified value? | 142-31,800 ohms | 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 heater and A/C controls. 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 LH air duct temperature sensor. Refer to Air Temperature Sensor Replacement - Left Side . Did you complete the replacement? | -- | Go to Step 12 | -- |
11 |
Important:: Perform the recalibration procedure for the heater and A/C controls. Replace the heater and A/C controls. 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 |
