Code C0579 indicates that the brake booster temperature sensor B signal circuit is reporting a voltage lower than the expected range to the control module. This sensor monitors temperature within or near the brake booster assembly, and a low-voltage reading typically suggests a short to ground, an open reference circuit, or a failed sensor rather than an actual overtemperature condition.
The sensor itself may have an internal short or open, pulling the signal voltage low or producing no output. This is the most common single cause for a circuit-low code on a dedicated sensor line.
The signal wire between the sensor and the control module may be chafed or pinched against a grounded surface, causing the module to read near-zero volts. Routing near the booster or chassis edges makes this fairly common.
Moisture intrusion, corrosion, or a pushed-back terminal at the sensor or module connector can interrupt the 5V reference or signal return, resulting in a low-voltage reading.
If the reference voltage feed or the sensor ground path is broken, the sensor cannot generate a valid signal and the module will interpret the input as circuit low.
An internal failure in the module that reads this sensor is possible but uncommon. It should only be considered after all wiring, connector, and sensor testing has ruled out external causes.
No. A circuit-low code means the sensor signal voltage is below the expected range, which is almost always an electrical fault rather than an actual temperature reading. The system cannot reliably determine booster temperature when this code is set.
In most cases braking performance is unaffected because this is a monitoring circuit, not a direct assist-control circuit. However, the brake warning lamp may be illuminated, and any underlying issue should be diagnosed to ensure no related brake system faults are present.
Almost never. C0579 is a sensor circuit code and the control module is the least likely cause. Replacing the module without confirming wiring, connector, and sensor integrity first is a common and expensive mistake. The module should only be suspected after all external testing is exhausted.
No. This code specifically refers to a temperature sensor associated with the brake booster assembly. Brake pressure, fluid level, and booster pressure codes use different DTC designations and should not be confused with C0579.