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DTC codes / U05xx · Network communication / U055F

U055FInvalid Data Received From Electronic Brake Booster Control Module A

U055F is a communication fault where the electronic brake booster control module (EBB) sends data that the vehicle's network rejects as invalid or implausible. The computer has detected that the messages from the brake booster module are missing critical parameters, out of range, or corrupted, so it cannot trust the booster's status for stability and braking assist functions.

SystemNetwork
Code typeGeneric (all makes)
SeverityHigh
Fix difficultyProfessional
AreaNetwork communication

Symptoms you may notice

  • Illumination of the brake system warning light, often accompanied by the traction control or stability control light.
  • A noticeable reduction or complete loss of brake assist, requiring significantly more pedal effort to stop the vehicle.
  • The stability control or hill-start assist system may become disabled, with a corresponding message on the driver information display.
  • An audible chime or warning message indicating a brake system fault or service required.
  • In some cases, the vehicle may enter a reduced-power limp mode or limit certain driver-assist features.
  • Often no symptoms besides the warning light, especially if the invalid data is intermittent and the booster still functions mechanically.

Common causes, most likely first

  1. A failing electronic brake booster control module that is internally corrupting or misreporting its data.
  2. Corroded, loose, or damaged wiring and connectors at the brake booster module or along the controller area network (CAN) bus.
  3. Low or unstable system voltage, often from a weak battery or failing alternator, causing the module to send out-of-range signals.
  4. A software glitch or outdated calibration in the brake booster module or another module on the same network.
  5. Water intrusion into the brake booster module connector or housing, leading to signal degradation.
  6. A fault in another module on the same CAN bus that is interfering with or corrupting the booster module's messages.
  7. Aftermarket accessories or poor previous repairs that have disturbed the network wiring or introduced electrical noise.

How to diagnose and fix it

  1. Perform a full scan of all modules and record all stored codes, then clear codes and test-drive to see if U055F returns immediately or only under specific conditions.
  2. Inspect the brake booster module connector and wiring for corrosion, loose pins, chafing, or water intrusion, and repair as needed.
  3. Test the battery and charging system under load to rule out low voltage as the root cause of invalid data.
  4. Check for technical service bulletins (TSBs) or software updates for the brake booster module and perform any applicable reprogramming.
  5. Using a scan tool with live data, monitor the brake booster module's data parameters for implausible values while operating the brake pedal and compare with known-good values.
  6. If wiring and power are confirmed good, substitute a known-good brake booster module or perform a module swap with proper programming to confirm the fault.
  7. After repairs, clear codes and perform a road test that includes braking and stability control activation to verify the code does not return.

When the booster module is not the culprit

  • A weak battery or failing alternator can cause the brake booster module to send invalid data without setting any charging system codes, so always load-test the battery first.
  • Corrosion inside the brake booster module connector is a common hidden cause, especially on vehicles driven in wet or salty conditions, and can mimic a failed module.
  • The code can be set by a faulty wheel speed sensor or steering angle sensor that shares the same CAN bus, because the booster module's data becomes implausible when it cross-checks against those inputs.
  • After replacing the brake booster module, some vehicles require a calibration or adaptation procedure that, if skipped, will immediately reset U055F.
  • Intermittent U055F codes that appear only in cold weather often point to a marginal solder joint inside the module rather than a wiring fault.

Can I keep driving with U055F?

If the brake warning light is on and you notice a hard pedal or reduced braking assist, stop driving and have the vehicle towed to a repair shop. If the only symptom is the warning light and braking feels normal, you may drive cautiously to a nearby mechanic, but avoid heavy braking or towing and do not ignore the warning.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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