DTC 100

DTC 100

CIRCUIT DESCRIPTION
- DTC 001 is for the mode actuator.
- DTC 100 is for the air temperature actuator.

The HVAC control module controls the HVAC door actuators to regulate the airflow through the 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 HVAC control module and controls the internal stepper motor. When a door positional change is required, the 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 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 001 Mode Actuator Failure
- DTC 100 Air Temperature Actuator Failure

CONDITIONS FOR RUNNING THE DTC
- Source voltage is 8.7-16.5 volts.
- The ignition is ON.

CONDITIONS FOR SETTING THE DTC
The actual door position is not near the commanded door position.

ACTION TAKEN WHEN THE DTC SETS
The HVAC control module does not command the actuator to move for the remainder of the ignition cycle.

CONDITIONS FOR CLEARING THE DTC
The DTC Clearing is performed. Refer to Diagnostic Trouble Code (DTC) Clearing. Accessing and Clearing Codes - HVAC System - Manual

DIAGNOSTIC AIDS
- If the condition is not present, refer to Diagnostic Aids for Circuit Testing and Wiring Repair procedures.
- If the DTC sets following a calibration of the door actuator, inspect the door and the actuator for the following conditions:
- A misaligned actuator
- Broken linkages or binding linkages
- A broken door or a binding door
- An obstruction that prevents the door from operating within the full range of motion
- Missing seals to the door
- Poor connections at the harness connector of the door actuator
- If both DTCs are present, then there is a circuit failure or a HVAC door actuator is pulling the 5-volt reference circuit low.

TEST DESCRIPTION

Steps 1 - 9:

Steps 10 - 19:

The numbers below refer to the step numbers on the diagnostic table.
2. The appropriate HVAC door actuator is the actuator that set the DTC. If both DTCs are present, then test the air temperature actuator. The air temperature actuator is easier to access.
7. This step simulates the output of the HVAC control module to drive the appropriate HVAC door actuator clockwise or counter clockwise.
8. Disconnecting each actuator, one at a time, isolates the disconnected actuators signal circuit from the 5-volt reference circuit that is common to all the actuators.