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C0048 — Brake Booster Travel Sensor

Generic OBD-II · all makesChassis

Code C0048 indicates a malfunction in the brake booster travel sensor or its circuit. This sensor measures brake pedal travel to help the vehicle's computer coordinate braking effort, particularly in vehicles with electronic or regenerative braking systems.

Symptoms

What causes it — most likely first

1. Faulty brake booster travel sensor

The sensor itself may have failed internally due to wear, moisture intrusion, or electrical breakdown, leading to out-of-range signals.

2. Wiring or connector issues

Corroded, chafed, or loose wiring and connectors at the sensor can interrupt the signal, power, or ground circuits.

3. Brake booster assembly failure

If the travel sensor is integrated into the brake booster assembly, a mechanical failure within the booster can cause improper sensor readings.

4. Mechanical binding in the pedal assembly

A sticking brake pedal pivot or improperly adjusted pushrod can cause physical travel discrepancies that trigger the sensor code.

5. Faulty control module (ABS/PCM)

A rare internal failure in the ABS or powertrain control module could prevent proper reading of the sensor signal. This is highly uncommon.

How it's diagnosed

  1. Scan all modules for additional codes to identify related faults in the ABS or braking system.
  2. Visually inspect the brake booster travel sensor, wiring harness, and connector for physical damage, corrosion, or loose pins.
  3. Use a digital multimeter to verify proper voltage, ground, and signal return at the sensor connector.
  4. Monitor the live data stream with a diagnostic scanner while pressing the brake pedal to check for erratic or flatlined sensor values.
  5. Test the brake pedal and booster pushrod for smooth, unobstructed travel and proper adjustment.
  6. If all wiring and mechanical components test normally, verify the sensor's resistance and output against manufacturer specifications before considering control module diagnosis.

Code facts & related codes

SystemChassis
StandardizationSAE generic — identical on every make

Frequently asked

Is it safe to drive with a C0048 code?

It is not recommended. The braking system may not function as intended, potentially resulting in a stiff pedal, reduced assist, or altered braking characteristics. Have it diagnosed immediately.

Will a C0048 code cause my vehicle to fail an emissions or safety inspection?

Yes, in most jurisdictions, an illuminated ABS or brake warning light will result in a failed safety inspection.

I was told to replace the PCM/ECM for this code. Is that correct?

No, that is almost always incorrect. The problem is overwhelmingly likely to be the travel sensor itself, the wiring, or the brake booster assembly. Control module failure is extremely rare and should only be suspected after all other components are thoroughly tested.

What exactly does the brake booster travel sensor do?

It measures how far the brake pedal is depressed and sends this data to the vehicle's computer. This allows the system to calculate the required amount of braking force, which is especially important for blending friction brakes with regenerative braking in hybrid or electric vehicles.