Principles of Operation

Heated Steering Wheel System Operation 

When a heated steering wheel request is received, the HSWM applies voltage and ground to the steering wheel heating element (integral to the steering wheel). The steering wheel is heated to a temperature of approximately 28-34 °C (82-94 °F) and is maintained by the HSWM using a temperature sensor (integral to the steering wheel). The HSWM supplies a reference voltage and ground to the temperature sensor and monitors the voltage drop for controlling current flow to the heating element. The HSWM is designed to remain on, heating the steering wheel and maintaining temperature until switched OFF on the FDIM or the ignition switch is turned OFF.

On all vehicles, slow heating between the 10 o'clock and 2 o'clock steering wheel hand positions is considered normal. On vehicles equipped with wood inserts in the steering wheel, there is no heating elements located under the inserts.

Heated Steering Wheel System Network Communication 

The controls and indicators for the heated steering wheel system are in are located in the FDIM (touch screen) only. The FDIM does not communicate on any network and is connected directly to the APIM.

When the FDIM controls are used, the APIM sends a heated steering wheel request message to the HSWM using the following message path:

• The APIM sends the request over the I-CAN to the FCIM.
• The FCIM sends the request over the I-CAN to the IPC module.
• The IPC module then sends the request to the BCM over the HS-CAN.
• Lastly, the BCM sends the requests to the HSWM over the MS-CAN.

The messaging path is followed in reverse for status updates that need to be sent from the HSWM to the APIM.

Remote Start System Behavior 

When the remote start feature is used, the heated steering wheel system may be configured, through the message center, to be activated by the HVAC module based on outside air temperature. During remote start, the outside air temperature is continually evaluated by the HVAC system and the heated steering wheel system activation changes if the outside air changes from cold to moderate or warm temperatures or back from moderate or warm to cold temperatures.

For cold ambient air temperatures (below 10 °C (50 °F)) the heated steering wheel activates if the steering wheel is set to Auto in the IPC message center.

For moderate and warm ambient air temperatures (above 10 °C (50 °F)) the heated steering wheel does not activate.

FET Protection 

A FET is a type of transistor, that used with module software, monitors and controls current flow on module outputs. For information on FET protection, refer to Multifunction Electronic Modules .