Steering Wheel Heater (LRH), Function - GF46.11-P-0001FR

Model 257, 290 

up to model year 2021 

with code 443 (Heated steering wheel) 

Courtesy of MERCEDES-BENZ USA

Function requirements, general 

• Circuit 15R ON
• Interior temperature below 30°C

The electronic ignition lock control unit sends the status of circuit 15 over the suspension FlexRay steering column tube module control unit and the steering wheel CAN to the steering wheel electronics.

The interior temperature value is sent by the climate control unit to the steering wheel electronics over the interior CAN electronic ignition lock control unit suspension FlexRay steering column tube module control unit and the steering wheel LIN.

Steering wheel heater, general 

It is possible to heat the steering wheel rim using the steering wheel heater. The steering wheel heater includes the following subfunctions:

• Manual switching on and off 
• Automatic switch off 

Manual switching on and off 

The steering wheel heater is operated via the steering wheel heater switch which is integrated in the steering column adjustment and steering wheel heater switch. The steering wheel heater is switched on or off by turning the steering wheel heater switch.

The steering column tube module control unit reads in the signals of the steering wheel heater switch directly and sends this over the steering wheel CAN to the steering wheel electronics. Based on this, the steering wheel electronics activates or deactivates the steering wheel heater heating element in the steering wheel rim.

The surface temperature of the steering wheel rim is detected by the heating element temperature sensor. The steering wheel electronics reads in the signals of the heating element temperature sensor directly and regulates the surface temperature of the steering wheel rim to 35°C.

The steering wheel electronics send the status of the steering wheel heater over the steering wheel CAN to the steering column tube module control unit. With activated steering wheel heater, the steering column tube module control unit actuates the steering wheel heater indicator lamp in the steering wheel heater switch directly.

Automatic switch off 

The steering wheel heater is switched off automatically if one of the following events occurs:

• Switch-off by timer control 

  The timer control is implemented by the steering wheel electronics. After expiry of a period of 15 minutes the steering wheel heater is switched off. The steering wheel heater timer control can be parameterized through the diagnosis tester.

• Shut-off in the event of a hardware defect 

  If actuation is activated without an appropriate request, the steering wheel heater is switched off and a fault message is stored in the fault memory.

• Switch-off in the event of overtemperature 

  If the vehicle interior temperature rises above 30 °C  , the steering wheel heater is switched off. The steering wheel heater indicator lamp remains on. If the vehicle interior temperature drops below 30 °C  , the steering wheel heater is switched on again automatically. The cutout temperature of the steering wheel heater can be parameterized through the diagnosis tester.

  The control unit for climate control sends the current interior temperature value over the interior CAN, electronic ignition lock control unit, suspension FlexRay, steering column tube module control unit and the steering wheel CAN to the steering wheel electronics.

  If no plausible interior temperature value is present, the outside temperature value is used instead.

• Switch-off in the event of a fault (short circuit, overload or line break) 

  In the event of a short circuit, an overload or a line break, the power supply of the steering wheel heater heating element is switched off. The exact source of the fault can be diagnosed using the diagnostic tester.

• Switch-off during engine start 

  The steering wheel heater is switched off briefly when the engine is started. The timer control continues running, the steering wheel heater indicator lamp also remains on. No undervoltage assessment takes place during startup.

• Switching off by means of energy management 

  To prevent a battery discharging, the state of charge is continuously evaluated. Depending on the situation, the steering wheel heater is also switched off if necessary.

  If the steering wheel heater is switched off, the steering wheel heater indicator lamp initially remains switched on. If the on-board electrical system reaches the specified voltage again within the following 3 minutes, the steering wheel heater is also automatically started. If the shutoff period lasts longer than 3 minutes, the steering wheel heater indicator lamp is also switched off. If the shutoff period continues and the steering wheel heater is requested again, the steering wheel heater indicator lamp lights up for 1.5 s before it then goes out.

• Switch-off after circuit 15R OFF 

  With circuit 15R OFF and circuit 15C ON, the timer control continues for 5 min. If circuit 15R is switched on again, the steering wheel heater is also switched on.

• Shutoff at end of diagnosis 

  After completing a diagnosis the steering wheel heater is then switched off.

	Function schematic of electrical system for steering wheel heater		PE46.11-P-2050-97XBA
	Overview of system components of comfort heating systems		GF91.30-P-9990FR