C1223: OBD-II code C1223 means the EBCM sees no signal from the left rear 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.
• Rear wheels can lock during hard braking and the brake pedal does not pulse during ABS events because interventions are unavailable.
• Vehicle stability control and electronic brake distribution are disabled, which can make the rear feel loose during aggressive stops.

Common causes

• A failed left rear wheel speed sensor — tip contaminated by brake dust or internal winding open — is the most common cause.
• Excessive play in the left rear wheel bearing or hub, common on higher-mileage vehicles, causes an unstable or missing signal.
• Damaged wiring along the trailing arm, a corroded connector inside the wheel well, or a rusted tone ring will also drop the signal.

What to do?

Scan the vehicle and check live wheel speed data during a slow road test. Rock the left rear wheel by hand to test the hub bearing for play. Swap the left and right rear sensors — if the fault moves to C1224, the sensor itself is faulty. Inspect the harness along the trailing arm for chafing and the connector for corrosion. Replace bearing, sensor, or repair wiring as indicated.