What it means
Left Rear Wheel Speed Sensor A Incorrect Component Installed: the installed component does not match the type the vehicle expects. Wheel-speed signals feed ABS, ESC, traction control and the speedometer.
At a glance
- Usually lights the ABS or stability-control warning light
- The engine or gearbox may go into limp mode
How it works
The left rear wheel speed sensor A provides wheel-speed information used by systems such as ABS, stability control, and traction control. C0557 indicates that the installed component may not match the type expected for that position, including a possible mismatch with the tone ring.
Common causes
Most likely first.
- Incorrect left rear wheel speed sensor installed
- Incorrect or mismatched tone ring
Symptoms
- ABS warning light on
- ESC/stability control deactivated
- Possible reduced brake assist
- Speedometer may behave erratically
How to diagnose it
- Record ABS or stability-control codes and freeze-frame data, then check live wheel-speed readings to see whether the left rear signal differs from the other wheels.
- Verify that the installed left rear wheel speed sensor A is the correct type for the vehicle using its parts and service information.
- Inspect the left rear sensor connector and wiring for damage, corrosion, looseness, or incorrect routing.
- Check the tone ring for damage, incorrect fit, or a mismatch with the installed sensor.
- Use the vehicle manufacturer's diagnostic procedure to confirm component compatibility and test the wheel-speed signal before replacing parts.
Common fixes
- Fit the correct left rear wheel speed sensor A if the installed unit is incompatible.
- Repair damaged wiring or connector terminals at the left rear sensor.
- Replace a mismatched or damaged tone ring if confirmed by inspection and vehicle-specific information.
- Clear the code and verify the left rear wheel-speed signal after the repair.
Can I keep driving?
ABS or stability control may be disabled or limited, and braking assistance may be affected; drive cautiously and leave extra stopping distance. Avoid hard braking where possible, and stop safely if braking behaviour changes.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.