C1221: OBD-II code C1221 means the EBCM sees no signal from the left front wheel speed sensor — ABS and stability control are disabled while active.

Symptoms

• The ABS, traction control, and stability control warning lamps illuminate together, usually above 5 mph as the EBCM checks for wheel signals.
• Wheels can lock during hard braking and the brake pedal does not pulse during ABS events because interventions are unavailable.
• On some Ford models the steering may feel heavier because the steering-angle and yaw-rate inputs are also affected by the loss of signal.

Common causes

• A failed left front wheel speed sensor — tip contaminated by debris or internal winding open — is the single most common cause.
• Excessive play in the left front wheel bearing or hub assembly lets the sensor-to-tone-ring gap vary too much for a stable signal.
• Damaged wiring at the strut, a corroded connector, or a rusted encoder ring on the CV joint will also drop the signal to zero.

What to do?

Scan the vehicle and check live wheel speed data during a slow road test. Rock the left front wheel by hand to test the hub bearing for play. Swap the left and right front sensors — if the fault moves to C1222, the sensor itself is bad. Inspect the harness where it clips to the strut for chafing and the connector for corrosion. Replace bearing, sensor, or repair wiring as indicated.