What does it mean?
C1243 is a Chassis (ABS, traction control, steering) fault code. It indicates: Acceleration Sensor Stuck Malfunction .
Symptoms
- Stability, traction and ABS lamps on and the stability system disabled
- Acceleration value on the scan tool that does not change during braking or acceleration
- Hill-hold assist not working, so the vehicle rolls back on a slope
- Stability control either never intervening or intervening at odd moments
- Fault stores again as soon as the code is cleared
Likely causes
- Internal sensing element seized or damaged, so the output no longer changes
- Water damage or condensation inside the sensor housing
- High resistance in the supply or ground circuit, leaving the sensor stuck at a fixed reading
- Connector partly unplugged or with a corroded terminal
- Sensor bolted down loose or on a distorted bracket, so it was calibrated in the wrong position
- Stale data on the network because the sensor has stopped updating its message
- Stability module reading and holding a default value after a failed calibration
How to fix it
- Watch the acceleration value live during a gentle road test with braking and acceleration; a completely flat trace confirms the stuck signal
- Measure supply voltage and ground quality at the sensor connector with the key on
- Inspect the connector for corrosion, moisture and pushed back terminals
- Check the sensor mounting bolts and the bracket, and confirm the orientation matches the design
- Check for water ingress in the mounting area under the carpet or console
- Run the calibration routine; a seized sensor will usually refuse to complete it
- Replace the sensor, then calibrate it and confirm the value now tracks vehicle movement