Possible causes

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

Symptoms

– ABS Warning Light ON

C0238 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 C0238 code