C0551: Longitudinal Acceleration Sensor Circuit/Open

What it means

Open circuit on the longitudinal acceleration sensor (used by ESP/ESC for braking-direction stability).

How it works

The longitudinal acceleration sensor measures vehicle movement along its direction of travel, and the stability-control module uses that information when managing braking and stability. C0551 sets when the sensor circuit is open and the module cannot receive its signal.

Common causes

Most likely first.

1. Wiring open
2. Pin pushed back out of connector body
3. Cracked solder joint inside the module or sensor

Symptoms

• Stability-control warning light on
• Traction or stability control may be limited

How to diagnose it

1. Scan the stability-control module, save freeze-frame data, and check whether the longitudinal acceleration reading is absent.
2. Locate the longitudinal acceleration sensor using vehicle service information and inspect its connector for a loose fit or backed-out pin.
3. Follow the sensor wiring toward the module and look for breaks, chafing, or damage at harness bends and mounting points.
4. Use the wiring diagram to check signal-circuit continuity and inspect terminal contact at both the sensor and module.
5. If the external circuit passes, investigate the sensor and module for an internal open or cracked solder joint using vehicle-specific procedures.

Common fixes

• Reconnect the longitudinal acceleration sensor or properly seat a displaced terminal.
• Repair an open or damaged section of the sensor wiring.
• Clean or replace damaged connector terminals and secure the harness.
• Replace or repair the sensor or module only if testing confirms an internal open.

Can I keep driving?

Stability or traction control may be limited, so drive gently and avoid slippery roads or abrupt manoeuvres. If the vehicle also shows a brake warning or behaves unpredictably, stop safely and seek assistance.