C0047: Brake Booster Pressure Sensor (Subfault)

What it means

This code identifies a fault associated with the brake booster pressure sensor. The specific failure depends on the diagnostic subtype.

At a glance

• Usually lights the ABS or stability-control warning light
• The engine or gearbox may go into limp mode

How it works

The brake booster pressure sensor reports pressure in the booster to the brake control system, which uses the reading to assess available brake assistance. This subfault code indicates a problem associated with that sensor, but the subtype is needed to determine the specific failure.

Common causes

Most likely first.

1. Faulty sensor
2. Damaged wiring or connector
3. Poor sensor power or ground

Symptoms

• Brake or ABS warning light
• Reduced brake assist may occur

How to diagnose it

1. Read the brake-related subtype and freeze-frame data to identify the reported failure and the conditions when it set.
2. Check live booster-pressure data during brake application and release for a missing, erratic, or implausible response.
3. Inspect the booster pressure sensor, its connector, and wiring for damage, corrosion, or loose terminals.
4. Check the sensor's power, ground, and signal circuits for opens or shorts against the wiring diagram and manufacturer's specification.
5. If the circuit checks pass, test the sensor and brake control module input using the manufacturer's diagnostic procedure.

Common fixes

• Repair damaged wiring or a loose or corroded sensor connector.
• Restore the sensor's power or ground connection.
• Replace the brake booster pressure sensor if its output fails testing.
• Repair the brake control module only if its input is confirmed faulty.

Can I keep driving?

Reduced brake assist may make the pedal require more effort, and the vehicle may enter a reduced-function mode. Avoid unnecessary driving; if the pedal is unusually hard or braking is impaired, stop safely and arrange assistance.