C0048: Brake Booster Travel Sensor (Subfault)

What it means

This code identifies a fault associated with the brake booster travel 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 travel sensor reports how far the booster mechanism moves, helping the control system assess brake-assist operation. This subfault code flags a problem associated with that travel sensor; the diagnostic subtype specifies the detected 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 subtype details and freeze-frame data to establish what failure the control system detected and when.
2. Monitor booster-travel data while applying and releasing the brake, checking for a signal that is absent, erratic, or does not track movement.
3. Inspect the travel sensor and its connector, and check the wiring for chafing, corrosion, or loose terminals.
4. Check the sensor's power, ground, and signal circuits for opens or shorts using the wiring diagram and manufacturer's specification.
5. If the circuit is intact, test the travel sensor and brake control module input using the manufacturer's procedure.

Common fixes

• Repair damaged wiring or clean and secure the sensor connector.
• Restore a poor power or ground connection to the travel sensor.
• Replace the brake booster travel sensor if it fails testing.
• Complete the manufacturer's calibration or learning procedure if required after service.
• Repair the brake control module only if its input is confirmed faulty.

Can I keep driving?

Brake assist may be reduced, so the pedal could take more effort to press. Avoid driving if pedal effort or braking changes; if the brakes feel normal, drive cautiously to a place where the fault can be diagnosed.