What it means
The brake booster temperature sensor B signal is below the expected range. 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 reports a temperature-related signal to the brake control system. The module sets C0579 when sensor B's circuit signal falls below its expected electrical range; that can result from the sensor circuit or its wiring, rather than proving the sensor itself has failed.
Common causes
Most likely first.
- Signal wire shorted to ground
- Connector pins corroded - high contact resistance
- Harness chafing through insulation
Symptoms
- Brake or ABS warning light
- Brake booster functions may be limited
How to diagnose it
- Scan the brake system for freeze-frame data and compare sensor B's live reading with sensor A or other available temperature data to confirm whether B is fixed low or changes with operating conditions.
- Inspect sensor B's connector and harness for chafing, exposed conductors, corrosion, or a wire contacting ground.
- Check the connector terminals for corrosion and secure pin contact, since poor contact can affect the signal.
- Using the wiring diagram and manufacturer's specification, test sensor B's signal for a short to ground and verify the sensor's supply and ground.
- If the circuit tests pass, compare sensor B's output with the manufacturer's specification and assess the sensor and module.
Common fixes
- Clean and secure corroded or loose sensor B connector contacts.
- Repair a signal wire shorted to ground.
- Replace or repair harness insulation damaged by chafing.
- Replace sensor B if its output fails the manufacturer's specification.
- Repair or replace the control module only if circuit and sensor tests identify it as the fault.
Can I keep driving?
If braking feels normal and the warning is limited to the brake or ABS system, drive cautiously and avoid situations that demand strong braking or stability control. Stop and arrange inspection if brake assist is reduced, the pedal changes, or another brake warning appears.
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.