Wheel Sensor 7/31, 7/32, 7/56, 7/57

GENERAL 

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Type 

Hall sensor (active sensor).

characteristic 

When the toothed wheel rotates, a pulsed current signal (square wave) with fixed pulse ratio is generated. The frequency increases with speed.

Tooth at sensor 

• I≈14 mA

Cover at sensor 

• I ≈ 7 mA

Other information 

Nothing

TERMINAL 

Front wheel sensor 

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Rear wheel sensor 

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Connector terminal	Control module terminal	Signal type	Miscellaneous
#1	#45	Power supply, front left	The sensor receives 12 V from the control module.
	#14	Signal output left front	Taxi signal. The signal can be used to check the wheel sensor's signal
#2	#46	Signal ground	The sensor is grounded through the control module.
#1	#36	Power supply, rear left	The sensor receives 12 V from the control module.
	#9	Signal output left rear	Taxi signal. Can be used to check the wheel sensor's function
#2	#37	Signal ground	The sensor is grounded through the control module.
#1	#34	Power supply, front right	The sensor receives 12 V from the control module.
	#11	Signal output right front	Taxi signal. Can be used to check the wheel sensor's function.
#2	#33	Signal ground	The sensor is grounded through the control module.
#1	#43	Power supply, rear right	The sensor receives 12 V from the control module.
	#7	Signal output right rear	Taxi signal. Can be used to check the wheel sensor's function.
#2	#42	Signal ground	The sensor is grounded through the control module.

CHECK 

Prerequisites (unless otherwise specified):

• Breakout box connected.
• Sensor engaged.
• Ignition switch position II.

Create a temporary voltage feed between #1 on the breakout box via a resistor of 1kΩ and the sensor's signal output (#7, #9, #11, or 14). Connect a voltmeter between the sensor's signal output and ground connection #16. Turn the wheel slowly:

Tooth against sensor U ≈ U_Low

Gap against sensor U ≈ U_bat

Direction sensitive wheel sensor 

There is a direction sensitive wheel sensor on the front right. The signal is made up in a slightly different way, see the appropriate service information for more information (Design and function, Brake control module (BCM)), but the method for measuring and the appearance of the pulse train is the same.

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