Circuit Description
The rear junction block supplies ignition voltage through circuit 141 (BRN). The HCM commands the actuator to move by suppling voltage on the command line circuit 1614 (DK GRN). The command line voltage and motor actions are as follows:
| • | 0 volts moves toward full hot. |
| • | 2.5 volts stops the motor. |
| • | 5 volts moves toward full cold. |
The HCM determines the current position by monitoring the voltage on the feedback circuit 1838 (PPL). A feedback potentiometer supplies a regulated 5-volt signal by the HCM on circuit 705 (GRY), and a ground from the HCM circuit 1791 (YEL). The pot is gear driven inside the actuator. The feedback voltage is a function of the motor position with a high voltage of 4-5 volts indicating full cold door position. A low voltage of less then 1 volt indicates the full hot position. Operation of the air mix door actuator can be evaluated through scan tool data.
The air inlet door motor is an electronic actuator stepper motor with a feedback potentiometer. The heater and A/C programmer determines the position of the door motor based on the voltage from the potentiometer. When the airflow is being recirculated, the voltage is low. When outside air is being admitted, voltage is high. The heater and A/C programmer controls the air inlet door motor to position the air inlet door in either the recirc or the fresh air positions as selected by the vehicle occupants.
Conditions for Setting the DTC
| • | The ignition is on. |
| • | The feedback circuit is open or shorted. |
Action Taken When the DTC Sets
| • | A default value of 128 counts will be used by the Heater and A/C programmer. |
| • | This default value results in only 2 positions of the actuator full outside air and full RECIRC air being used by the system. |
Conditions for Clearing the DTC
| • | Use a Scan Tool . |
| • | A history DTC will clear after 50 consecutive ignition cycles have occurred without a malfunction. |
| • | Battery voltage to the body control module is interrupted. |
Test Description
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Perform the Body Control Module (BCM) Diagnostic System Check before continuing with the diagnosis of this DTC.
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This step determines if the passenger temperature control is operating properly.
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This step ensures that the DTC was not set in error.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Did you perform the BCM Diagnostic System Check? | -- | Go to Step 2 | Go to Diagnostic System Check - Body Control System in Body Control System | |
Are the resistances near the specified ranges? | Full Cold - 1 kohms MID - 5 kohms Full Hot - 9 kohms Reset 90 kohms | Go to Step 3 | Go to Step 7 | |
3 |
Does the voltage measure near the specified value? | 5 V | Go to Step 4 | Go to Step 5 |
Did the DTC reset? | -- | Go to Step 9 | ||
5 | Test for continuity between the passenger temperature control assembly harness connector terminal 8 and the heater and A/C programmer connector terminal C15. Refer to Testing for Continuity in Wiring Systems. Is continuity present? | 5 V | Go to Step 8 | Go to Step 6 |
6 | Repair the open in CKT 1812 (TAN). Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to Diagnostic System Check - Body Control System in Body Control System | -- |
7 | Replace the passenger temperature control assembly. Refer to Control Assembly Replacement . Is the repair complete? | -- | Go to Diagnostic System Check - Body Control System in Body Control System | -- |
8 | Repair an open in CKT 831 (DK BLU/WHT). Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to Diagnostic System Check - Body Control System in Body Control System | -- |
9 |
Is the repair complete? | -- | Go to Diagnostic System Check - Body Control System in Body Control System | -- |
