Network Message Chart - Module Network Input Messages
| Broadcast Message | Originating Module | Message Purpose |
|---|---|---|
| PTC Relay Command | HVAC Module | This message contains the request for the electric booster heater relays to energize. |
| Engine coolant temperature | PCM | This message contains raw value from the engine coolant temperature. |
| Ambient air temperature | PCM | This message contains raw value from the ambient air temperature sensor. |
| PTC Heater Command | HVAC Module | This message contains the request for the electric booster heater auto, on and off command. |
Electric Booster Heater Operation
The electric booster heater ensures that the passenger compartment can be quickly warmed up when ambient temperatures are low. It is a heater element made up of ceramic resistors that is mounted in the climate control housing. It directly heats the airflow into the passenger compartment rapidly in the case of low ambient temperatures.
The current is switched via three electric booster heater relays located in the BJB / BCMC. The HVAC module sends a request message over the MS-CAN network to the GWM. The BCMC receives a network message over the HS-CAN1 requesting to apply power and ground to energize the relays. The electric booster heater is supplied voltage from the relays and has a dedicated ground circuit.
The HVAC control module energizes the electric booster heater relays when the operating parameters have been met. The electric booster heater relays are activated or deactivated individually or together by the HVAC control module as needed.
Electric booster heater operating parameters:
- Engine is running
- HVAC controls have been switched to the highest temperature setting
- Engine coolant temperature is below approximately 75deg.C (167deg.F)
- Ambient air temperature is below approximately 12deg.C (53.6deg.F)
- Sufficient generator capacity is available
The electric booster heater is deactivated when an engine coolant temperature of approximately 85deg.C (185deg.F) or an ambient air temperature of approximately 15deg.C (59deg.F) is exceeded.