CAN network

U0418 — Invalid Data Received from Brake System Control Module

Severity: medium Drive with care, to a shop

What U0418 means

U0418 means a control module on the network received messages from the brake system control module that are out of range or inconsistent. The ABS/ESP module normally broadcasts wheel speed, brake pressure and stability control status over the CAN bus. When that data looks invalid, other modules stop trusting it and shut down the features that depend on it.

Symptoms

  • Brake, ABS or stability control warning light on
  • Adaptive cruise control disabled
  • Several warning lamps on at once
  • Features of the affected module unavailable
  • Code may come and go

Possible causes

  1. Faulty brake control module (ABS/ESP)
  2. Faulty brake pressure sensor
  3. Corrupted CAN messages
  4. Open, shorted or chafed CAN bus wiring
  5. A faulty module loading down the bus
  6. Corroded connectors or terminals
  7. Power supply or ground fault at a module

How to diagnose

  1. Run a full-module scan to see which modules respond and which report communication faults
  2. Record all related codes and freeze frame data
  3. Check battery voltage and charging system output
  4. Measure CAN bus resistance and voltages at the diagnostic connector
  5. Inspect the harness and connectors at the brake module for corrosion and chafing
  6. Check power feeds, grounds and fuses for the ABS/ESP module
  7. Review brake pressure and wheel speed sensor data with a scan tool
  8. Disconnect suspect modules one at a time, only following a documented factory procedure

Common fixes

  • Repair or replace damaged CAN wiring
  • Clean or replace corroded terminals and connectors
  • Correct the power or ground fault at the module
  • Replace the brake pressure sensor
  • Replace or reflash the brake control module
  • Replace a faulty module that is disrupting the bus

Questions and answers

What does U0418 mean?

It is a communication fault: the brake system module is sending data that other modules consider invalid. The cause may be the module itself, the CAN bus or a power problem.

Can I drive with code U0418?

Briefly and carefully, yes, as the base brakes usually work. However ABS, stability control and cruise control may be off, so have it checked as soon as you can.

Do I need to replace the ABS module right away?

No. Check power, grounds, wiring and the CAN bus first, since those are the most common causes. Replace the module only after ruling them out.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.