DTC Description: Description

The mode door motor, air mix door motor, and intake door motor receive position commands from the front air control and report actual door position back via an LCU (Local Control Unit) installed inside each motor. Each door motor LCU has a unique address. The front air control communicates with the door motor LCUs by using each door's unique communication address. The front air control sends requested door position commands to each door motor LCU via a Local Interconnect Network (LIN) communication line using a communication protocol called LIN 2.0. The LIN-Bus is a vehicle bus standard used within current automotive network architectures. The LIN specification is enforced by the LIN-consortium, with the first exploited version being 1.1, released in 1999. Since then the specification has evolved to version 2.1 to meet current networking needs. The LCUs read the door positions from Position Balanced Resistors (PBR), also part of the motor, and returns that information to the front air control. The LCUs switch the polarity of the circuits connected to the DC motors to drive the motor forward or backward as requested by the front air control. The mode door has 5 expected positions and, therefore, can set up to 5 DTCs if the expected position is not reported back to the front air control. The air mix door motor and the intake door motor both have 2 DTCs related to being out of range. The front air control provides a voltage signal and receives a signal return from the LIN. The 3 motors share a common ground which completes the LIN infrastructure. If the signal return line shorts to ground or has an open before reaching any of the LCUs, the front air control will trigger DTCs for all the motors. Loss of the supplied voltage and common ground will also trigger all the motor DTCs.