What it means
The booster temperature signal is below the lower diagnostic threshold. Typical causes are a shorted sensor element or a short to ground in the harness.
At a glance
- Usually lights the check-engine light
How it works
Brake Booster Temperature Sensor A measures temperature at the electric brake booster for the assist controller. This code sets when Sensor A's signal drops below the allowed range, often because the sensor is internally shorted or its signal wire is grounded.
Common causes
Most likely first.
- Internal short in the sensor element
- Sensor signal wire shorted to ground
- Connector pins corroded - high contact resistance
Symptoms
- Brake-booster warning or reduced brake assist may occur
How to diagnose it
- Scan for booster-related codes and record freeze-frame data and Sensor A's live reading to confirm when the low signal occurs.
- With the vehicle safely parked, check for a brake-assist warning or increased pedal effort.
- Inspect Sensor A's connector and signal wire for corrosion, damaged insulation, or contact with ground.
- With the sensor disconnected as specified by the manufacturer, test the signal wire for a short to ground and inspect the connector terminals.
- Test Brake Booster Temperature Sensor A using the manufacturer's procedure to distinguish a failed sensor from a harness fault.
Common fixes
- Repair a Sensor A signal wire shorted to ground.
- Clean or repair corroded or loose connector terminals.
- Replace Sensor A if its element is internally shorted.
- Repair damaged wiring between the booster sensor and controller.
Can I keep driving?
The booster controller may reduce assist because Sensor A's temperature signal is too low, which can increase pedal effort and stopping distance. Do not drive if braking feels abnormal or assist is reduced; arrange prompt diagnosis.
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.