Possible causes

– Faulty Left Front Speed Sensor
– Left Front Speed Sensor harness is open or shorted
– Left Front Speed Sensor circuit poor electrical connection
– Faulty EBCM

Symptoms

– ABS Warning Light ON

C0227 GMC Description

As the wheel spins, the wheel speed sensor produces an Alternating Current (AC) signal. The Electronic Brake Control Module (EBCM) uses the frequency of the AC signal to calculate the wheel speed.

GMC Technical Service Bulletins for C0227 code