C0551 code meaning
Longitudinal Acceleration Sensor Circuit/Open
What C0551 means
C0551 reports an electrical break in the longitudinal acceleration sensor circuit: the brake or stability module no longer gets a usable fore-aft signal, usually because the signal or supply wire is open or a plug has lost contact. Earlier layouts mounted a separate g-sensor close to the centre of gravity and cabled it to the ABS unit; a Kelsey-Hayes patent (now ZF) describes a capacitive element whose analog voltage rises with acceleration and moves it onto the ABS circuit board to drop wiring and connectors. No manufacturer explains C0551 in a public document. Without the input, four-wheel-drive ABS loses its wheel-independent speed reference and stability functions are normally switched off with ABS/ESC lamps lit, while base braking remains. C0553 and C0554 cover a low or high voltage, C0552 an implausible value.
C0551 at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modePossible
- Repair difficultyMedium
- Typical labor0.5 to 2.5 hours
- Clears after repairWhen cleared with a scanner
Symptoms of C0551
- ABS and/or ESC warning lamp on
- Stability, traction or hill-start assistance unavailable
- ABS on four-wheel-drive vehicles regulates less precisely
Common causes of C0551
- Most likelyBroken signal or supply wire between sensor and brake module
- PossibleCorroded, loose or pushed-back terminal at the sensor plug
- Less likelyInternal open in the sensor or, on integrated designs, in the ABS/ESC unit
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Longitudinal accel sensorSensor wiring
What each part of C0551 means
| C | Chassis system: brakes, ABS, steering and suspension. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 51 | The exact fault in that area. |
What to do next
- Note C0551 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about C0551
What does C0551 mean?
C0551 means "Longitudinal Acceleration Sensor Circuit/Open". C0551 reports an electrical break in the longitudinal acceleration sensor circuit: the brake or stability module no longer gets a usable fore-aft signal, usually because the signal or supply wire is open or a plug has lost contact. It is a generic code, so it means the same on every make.
Is it safe to drive with C0551?
Drive gently and only to a workshop. With C0551 the car can go into limp mode (reduced power) to protect itself.
Will C0551 fail an emissions test?
C0551 is not an emissions code, so on its own it usually does not fail an emissions test. Other stored codes or a lit check engine light still can.
How hard is C0551 to fix?
Difficulty: medium. A typical repair takes 0.5 to 2.5 hours of work. This is a job for a workshop.
Will C0551 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.