Front-Wheel Sensors

Front-wheel sensors





The front left wheel sensor sends a wheel-speed signal to pin 7 on the control module. The sensor is grounded via pin 6.
The front right wheel sensor sends a wheel-speed signal to pin 5 on the control module. The sensor is grounded via pin 3.
The sensor unit has a toothed wheel with 29 teeth and an inductive sensor.
The inductive sensor works like a small alternator, the sine-wave voltage of which increases with increasing wheel speed. The sinewave voltage alternates between positive and negative polarity, which is achieved by alternate teeth and gaps on the tooth wheel. The control module uses this change of polarity as a pulse sensor. The frequency of the pulses increases with the speed the wheel.
With a multimeter set for AC voltage connected between the two leads of the sensor, a reading of >100 mVAC should be obtained when the wheel is rotated one revolution per second
A wheel speed of 20 km/h gives about 5 VAC.

The distance between the sensor and the toothed wheel should be 0.3-1.2 mm. This distance is adjustable. The control module uses the frequency to measure the vehicle speed.

Diagnostics





If there is a break in the front left circuit, diagnostic trouble code C1372 is set, the ABS function is disabled and the ABS warning lamp lights up. C1372

In the event of a mechanical fault or malfunction in the front left circuit, diagnostic trouble code C1371 is set, the ABS function is disabled and the ABS warning lamp lights up. C1371

If there is a break in the front right circuit, diagnostic trouble code C1377 is set, the ABS function is disabled and the ABS warning lamp lights up. C1377

In the event of a mechanical fault or malfunction in the front right circuit, diagnostic trouble code 1376 is set, The ABS Function is disabled and the ABS warning lamp lights up. C1376