Heating Ventilation Air Conditioning (HVAC) Module - Dual Automatic Temperature Control (DATC)

The Dual Automatic Temperature Control (DATC) system uses a remote Heating, Ventilation, and Air Conditioning (HVAC) module that is separate from the control interface. For details on the Heating, Ventilation, and Air Conditioning (HVAC) module communication, REFER to CONTROL SYSTEM LOGIC .

The Heating, Ventilation, and Air Conditioning (HVAC) module also controls the outputs for the interior ambient lighting, rear window defrost and heated seats.

The Heating, Ventilation, and Air Conditioning (HVAC) module utilizes an Field-Effect Transistor (FET) protective circuit strategy for its actuator outputs. Output load (current level) is monitored for excessive current (typically short circuits) and is shut down (turns off the voltage or ground provided by the module) when a fault event is detected. A short circuit Diagnostic Trouble Code (DTC) is stored at the fault event and a cumulative counter is started.

When the demand for the output is no longer present, the module resets the Field-Effect Transistor (FET) circuit protection to allow the circuit to function. The next time the driver requests a circuit to activate that has been shut down by a previous short (Field-Effect Transistor (FET) protection) and the circuit is still shorted, the Field-Effect Transistor (FET) protection shuts off the circuit again and the cumulative counter advances.

When the excessive circuit load occurs often enough, the module shuts down the output until a repair procedure is carried out. The Field-Effect Transistor (FET) protected circuit has 3 predefined levels of short circuit tolerance based on the harmful effect of each circuit fault on the Field-Effect Transistor (FET) and the ability of the Field-Effect Transistor (FET) to withstand it. A module lifetime level of fault events is established based upon the durability of the Field-Effect Transistor (FET). If the total tolerance level is determined to be 600 fault events, the 3 predefined levels would be 200, 400 and 600 fault events.

When each tolerance level is reached, the short circuit Diagnostic Trouble Code (DTC) that was stored on the first failure cannot be cleared by a command to clear the Diagnostic Trouble Codes (DTCs). The module does not allow the Diagnostic Trouble Code (DTC) to be cleared or the circuit to be restored to normal operation until a successful self-test proves that the fault has been repaired. After the self-test has successfully completed (no on-demand Diagnostic Trouble Codes (DTCs) present), Diagnostic Trouble Code (DTC) U1000:00 and the associated Diagnostic Trouble Code (DTC) (the Diagnostic Trouble Code (DTC) related to the shorted circuit) automatically clears and the circuit function returns.

When each level is reached, the Diagnostic Trouble Code (DTC) associated with the short circuit sets along with Diagnostic Trouble Code (DTC) U1000:00. These Diagnostic Trouble Codes (DTCs) can be cleared using the module self-test, then the Clear Diagnostic Trouble Code (DTC) operation on the scan tool. The module never resets the fault event counter to zero and continues to advance the fault event counter as short circuit fault events occur.

If the number of short circuit fault events reach the third level, then Diagnostic Trouble Codes (DTCs) U1000:00 and U3000:49 set along with the associated short circuit Diagnostic Trouble Code (DTC). Diagnostic Trouble Code (DTC) U3000:49 cannot be cleared and a new module must be installed after the repair.

The Heating, Ventilation, and Air Conditioning (HVAC) requires Programmable Module Installation (PMI) when it is replaced.