Circuit Description
The following DTCs are for the HVAC door actuators:
| • | B0429 is for the auxiliary air temperature actuator. |
| • | B3531 is for the auxiliary mode actuator. |
The auxiliary HVAC control module controls the auxiliary HVAC door actuators to regulate the airflow through the auxiliary HVAC system. Each actuator consists of a stepper motor, a logic circuit, and a potentiometer. The potentiometer inside the door actuator allows the module to monitor the current position of the actuator drive shaft. The logic circuit inside the actuators receives control signals from the auxiliary HVAC control module and controls the internal stepper motor. When a door positional change is required, the auxiliary HVAC control module calculates a commanded door position. The module compares the commanded door position to the actual door position and determines the needed direction of motor rotation. The module applies a signal voltage to the door control circuit that is an input to the internal logic circuit of the door actuator. A 5-volt signal increases the door position. A 0 volt signal decreases the door position. When the commanded door position is equal to the actual door position, the auxiliary HVAC control module sends a 2.5-volt signal to the door actuator and motor rotation stops. The ignition 3 voltage circuit provides source voltage to the logic circuit. The module provides ground to the actuator logic circuit through the low reference circuit.
DTC Descriptors
This diagnostic procedure supports the following DTCs:
| • | DTC B0429 Temperature Control 3 Circuit Range/Performance |
| • | DTC B3531 Air Flow Control 10 Circuit |
Conditions for Running the DTC
| • | Source voltage is 8.7-16.5 volts. |
| • | The ignition is ON. |
| • | The auxiliary HVAC control module commands the actuator to move. |
Conditions for Setting the DTC
The actual door position is not near the commanded door position.
Action Taken When the DTC Sets
The auxiliary HVAC control module does not command the actuator to move for the remainder of the ignition cycle.
Conditions for Clearing the DTC
| • | The DTC becomes history during the next ignition cycle in which the auxiliary HVAC control module no longer detects a stall condition. |
| • | The history DTC will clear after 100 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. |
| • | Inspect the appropriate door and door actuator for the following conditions: |
| - | A misaligned door actuator |
| - | A binding door |
| - | An obstruction that prevents the door actuator from operating within the full range of motion |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
Determines if the auxiliary HVAC door actuator is stalled.
-
Applies control circuit voltages to the input of the auxiliary HVAC door actuator.
Step | Action | 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 | ||||||
Does the scan tool indicate that the value of the Aux. Temp Dr. Position or the Mode Door Actual parameter changes? | Go to Diagnostic Aids | Go to Step 3 | |||||||
Does the drive shaft of the appropriate auxiliary HVAC door actuator rotate? | Go to Step 8 | Go to Step 4 | |||||||
4 | Test the door control circuit of the appropriate auxiliary HVAC door actuator for a short to voltage and for a short to ground. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 13 | Go to Step 5 | ||||||
5 |
Does the test lamp illuminate? | Go to Step 6 | Go to Step 10 | ||||||
6 | Inspect the appropriate auxiliary HVAC door and the door actuator for the following conditions:
Did you find and correct the condition? | Go to Step 13 | Go to Step 7 | ||||||
7 | Inspect for poor connections at the harness connector of the appropriate auxiliary HVAC door actuator. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 13 | Go to Step 11 | ||||||
8 | Test the door control circuit of the appropriate auxiliary HVAC door actuator for an open. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 13 | Go to Step 9 | ||||||
9 | Inspect for poor connections at the harness connector of the auxiliary HVAC control module. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 13 | Go to Step 12 | ||||||
10 | Repair the ignition 3 voltage circuit of the appropriate auxiliary HVAC door actuator. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 13 | -- | ||||||
11 |
Important: Perform the calibration procedure for auxiliary HVAC door actuators. Replace the appropriate auxiliary HVAC door actuator. Refer to the appropriate replacement procedure: Did you complete the replacement? | Go to Step 13 | -- | ||||||
12 | Replace the auxiliary HVAC control module. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement? | Go to Step 13 | -- | ||||||
13 |
Does the DTC set again? | Go to Step 2 | System OK | ||||||
