What it means
The brake booster temperature sensor B signal is intermittent or erratic. The code alone does not identify whether the cause is the sensor or its circuit.
At a glance
- Usually lights the ABS or stability-control warning light
How it works
Brake booster temperature sensor B sends a signal that the brake control module monitors over time. C057D sets when that signal from sensor B cuts in and out or changes erratically, often because a connector or harness connection is unstable.
Common causes
Most likely first.
- Connector loose
- Connector with intermittent contact under vibration
- Harness routed against vibrating component
Symptoms
- Brake or ABS warning light
- Brake booster functions may be limited
How to diagnose it
- Review freeze-frame data and monitor sensor B's live reading while the vehicle is stationary to see whether it jumps or drops out.
- Inspect sensor B's connector lock, terminals, and harness routing for looseness, corrosion, chafing, or contact with a vibrating component.
- With the vehicle safely parked, gently move the connector and harness while watching the live reading for dropouts.
- Use the wiring diagram and manufacturer's procedure to check continuity and terminal contact while flexing the suspect section of sensor B's wiring.
- If the signal remains erratic with a sound harness and connector, test sensor B and the module input to the manufacturer's specification.
Common fixes
- Secure the loose sensor B connector.
- Clean or repair connector terminals with intermittent contact.
- Repair chafed wiring or reroute it away from a vibrating component.
- Replace sensor B if its output remains intermittent after circuit repairs.
- Repair or replace the control module only if the manufacturer's tests confirm an input fault.
Can I keep driving?
Drive cautiously and avoid situations where a sudden loss of brake-booster function would be hazardous. If assist or pedal feel changes, stop safely and arrange inspection.
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.