Possible causes

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

Symptoms

– ABS Warning Light ON

C0221 CADILLAC 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.

CADILLAC Technical Service Bulletins for C0221 code