C0048 Brake Booster Travel Sensor

Covers the travel (position) sensor of the power brake booster or brake actuation unit, which reports how far the booster input rod or piston has moved so the module can match assist to driver demand. The module monitors the sensor for a signal outside the valid range, an open or short and a position that is implausible against pedal position or boost pressure. It complements the booster pressure sensor C0047: travel gives displacement while pressure gives force, and together they let the module close the assist loop in electronic and brake-by-wire boosters. A fault reduces or disables controlled assist, changes pedal feel and sets the brake or ABS warning lamp while base braking remains. Patents describe an electrical travel sensor that tracks the moving wall inside a vacuum booster. No manufacturer documents this code publicly.

Likely causes

Symptoms

• Changed brake pedal feel
• Reduced or inconsistent brake assist
• ABS or brake warning lamp on

Repair estimate

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

Related codes

References: patents.google.com, en.wikipedia.org, en.wikipedia.org.