C057B: Brake Booster Temperature Sensor B Circuit/Open

What it means

The brake booster temperature sensor B circuit is open or lacks electrical continuity. The module may not receive a valid temperature signal.

At a glance

• Usually lights the ABS or stability-control warning light

How it works

Brake booster temperature sensor B sends a signal through its circuit to the brake control module. C057B indicates that the module detects an open circuit or loss of continuity, so it may not receive a valid temperature signal from sensor B.

Common causes

Most likely first.

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

Symptoms

• Brake or ABS warning light
• Brake booster functions may be limited

How to diagnose it

1. Scan the brake system for freeze-frame data and related codes, and check whether sensor B's live value is missing or fixed at a default reading.
2. Inspect sensor B's connector and harness for a disconnected plug, broken wire, corrosion, or a terminal pushed back into the connector body.
3. Confirm the connector is locked and the pins make firm contact, since an incomplete connection can leave the circuit open.
4. Using the wiring diagram, test continuity in sensor B's signal circuit and check its supply and ground against the manufacturer's specification.
5. If the harness and connector pass, test sensor B and the module connections as specified by the manufacturer.

Common fixes

• Reconnect and secure sensor B's connector.
• Repair or replace a damaged signal wire.
• Clean or repair corroded or recessed connector terminals.
• Replace sensor B if it has an internal open circuit confirmed by testing.
• Repair or replace the module only if the sensor circuit and sensor test correctly.

Can I keep driving?

If braking feels normal, drive cautiously and avoid relying on full brake-booster functions until the fault is checked. Stop safely if assist is reduced, the pedal becomes unusually hard, or other brake warnings appear.