C0047 indicates the brake or powertrain control module has detected an out-of-range, implausible, or failed signal from the brake booster pressure sensor. This sensor reports the vacuum or pressure available to power the brake booster. A stored code can illuminate warning lamps and may reduce or disable brake assist.
The sensor itself is the most common source of the code; its internal element or circuitry can drift, stick, or fail outright and report an incorrect pressure reading.
A cracked, disconnected, or collapsed hose between the intake manifold and booster can make actual booster vacuum differ from what the sensor expects, setting a performance code.
Corroded, chafed, or loose terminals in the sensor harness can cause intermittent or fixed incorrect voltage, producing an out-of-range fault.
On vehicles with an electric or engine-driven auxiliary vacuum pump, weak or absent pump output can cause low booster pressure and trigger the sensor code.
A failed ABS, brake, or powertrain control module is uncommon for this code and should only be considered after the sensor, vacuum system, and wiring have been ruled out.
The code refers to the sensor circuit, but the root cause may be a vacuum leak, hose restriction, wiring fault, or failed vacuum pump rather than the sensor itself.
Braking effort may increase significantly and stopping distances can lengthen; have the system inspected promptly and avoid extended or high-speed driving until repaired.
Usually no. Control module failure is rare for this code. The sensor, vacuum hoses, check valve, pump, and wiring should be thoroughly diagnosed first.
The booster may not be receiving or holding enough vacuum, so the sensor reports low pressure and the system may disable or reduce power brake assist.