C1228: OBD-II code C1228 flags an erratic right rear wheel speed signal — the EBCM sees brief drops or spikes and disables ABS intermittently.

Symptoms

• The ABS and traction control warning lamps illuminate intermittently, usually only while driving, and may clear after an ignition cycle before returning.
• The ABS can activate at low speeds when it shouldn't, or feel erratic, and the brake pedal may pulse unexpectedly during light braking.
• Stability control and electronic brake distribution can trigger inappropriately, which may make the rear feel loose during aggressive stops.

Common causes

• Missing teeth or damage on the right rear reluctor or tone ring create momentary dropouts as the sensor rotates past the damaged section.
• Excessive lateral play in the right rear wheel bearing lets the sensor gap vary during cornering, causing signal amplitude variation.
• A partially failing sensor producing a noisy signal, brake dust or debris on the sensor tip, or mismatched tire sizes across the axle can also trigger it.

What to do?

Compare all four wheel speeds in live data during a road test — the errant wheel will show brief drops or spikes while the others read steadily. Inspect the reluctor or tone ring visually for chipped teeth. Check the rear wheel bearing for play. Clean any brake dust or metallic debris off the sensor tip. Replace the sensor, hub, or tone ring depending on findings, and confirm tire sizes match across the axle.