C1284: OBD-II code C1284 flags an out-of-range bias on the lateral accelerometer — the sensor's stationary zero reading is drifting beyond acceptable limits.

Symptoms

• ABS, traction control, and stability control lamps illuminate together and remain on continuously.
• Stability control interventions are disabled because the EBCM cannot trust the lateral-acceleration input.
• Standard braking and ABS remain functional; only electronic stability control is affected.

Common causes

• A drifting or ageing lateral accelerometer (often integrated with the yaw rate sensor) that no longer reads zero when stationary.
• A loose sensor mounting bracket or damaged sensor bolt allowing physical tilt that biases the accelerometer reading.
• Missing lateral-accel zero-point calibration after sensor replacement or major suspension work.

What to do?

With the vehicle level and stationary, read live lateral acceleration — it should be within a few hundredths of a g of zero. If biased, perform the sensor zero-point calibration with a scan tool. If calibration will not complete, the sensor has failed and needs replacement.