U0129 U0129 is a generic network code: a module on the vehicle network lost communication with the brake control module (ABS or stability module), usually stored by the engine, body or instrument computer

Lost communication with brake control module

U0129 in short

U0129 means another computer on the vehicle network lost contact with the brake control module, the ABS and stability module. Owners report red brake, ABS and traction lights with it. Because brakes are involved, have a technician read all codes and check that module soon; do not try to fix it yourself.

The brake control module (ABS or stability module) shares speed and brake data with the engine, transmission and instrument computers. When the others stop hearing it, they store U0129. The code names the missing module, not the faulty part.

Owner reports pair it with ABS, brake, traction and power steering warnings, and one Toyota bulletin summary for Tundras with U0129 and P0500 says to replace the brake actuator assembly. Other reports point at a harness or power problem, so the module is not the only suspect.

Because the brake system is involved, this page explains the code only and gives no repair steps.

Most likely causes

  1. Brake control module or actuator failure

    Supported by vehicle data
    Why it ranks here
    A Toyota Tundra bulletin summary for U0129 with P0500 says to replace the brake actuator assembly, and a Camry owner reports dealer codes C1249 and U0129 together.
    What would change this
    Rises if the brake module has its own stored codes or no communication on a scan. Falls if power, ground or wiring problems are found first.
    How to test the brake system control module (abs module)

  2. Wiring, connector or power problem on the network

    Common general cause
    Why it ranks here
    TaT lists the code only as a lost-communication definition, and lost-communication codes generally can come from power, ground, wiring or other modules; a GM bulletin summary for U0129 describes an engine harness short.
    What would change this
    Rises if several unrelated modules also lost communication or the codes are intermittent. Falls if only the brake module is silent.

  3. Another module disturbing the network

    Possible — needs testing
    Why it ranks here
    A 2024 Accord Hybrid owner was told an intermittent camera was behind many codes including U0129, and a 2017 CR-V owner was told an A/C control unit was behind it; two single reports do not make a pattern.
    What would change this
    Rises if a failing module on the same network is found. Falls if the brake module tests bad.

What to test first

Start at step 1. Each result tells you what it means and where to go next.

  1. Read every stored code from all modules, and note whether the brake module also stores codes and whether other U-codes appear.

    Low riskTool: scan tool that reads all modules

    • IfThe brake module stores its own codes, or many modules lost communication at once

      It meansThe module or a shared network problem is involved; a technician should check power, ground and the network.

      Go to step 2

    • IfOnly U0129 is stored and it will not come back after clearing

      It meansIt may have been a one-off; keep watching and have it checked if lights return.

  2. Have a brake and network specialist check the brake module power, ground, connectors and network signals, and ask for a bulletin check for the exact car.

    Best left to a shop

    Warning:Brake and ABS repairs affect stopping ability; leave testing and repair to a trained technician.

Symptoms

  • Red brake, ABS, traction or power steering warning lights
  • Brake pedal feel changes or the car revs against the brake Gets more serious: stop and have it checked.
  • Check engine light with U0129 stored

How to fix

This is a safety-critical system, so we explain the code but don't give repair steps. Have it inspected by a qualified technician.

Parts and cost context

  • Brake system control module (ABS module):Reports for this code involve the brake actuator or module, but replacement should follow a technician confirming the fault; labor varies; get a quote.

Labor varies by vehicle and shop; get a quote before you approve a repair.

Compare used part prices on PartPriceGuide

On your vehicle

Toyota

  • TSB-0325-08Status unverified

    ABS, brake or 4WD light on with U0129 and P0500

    2007–2008tundra · issued · NHTSA 10027745

    Says to replace the brake actuator assembly when those codes set. Only the NHTSA summary was read.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

Chevrolet

  • 2019–2020 · Silverado 1500

    Supported by vehicle data

    A bulletin summary lists U0129 under an engine harness short; a 2019 owner also reports it.

  • PIT5713Status unverified

    Engine wiring harness shorting at the left front cylinder head

    2019–2020silverado-1500 · issued · NHTSA 10165919

    Preliminary information on a harness short that causes sweeping gauges and warning messages. Only the NHTSA summary was read.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

Honda

  • U0122U0122 is a generic network code: a module lost communication with the vehicle dynamics control module, which runs stability control and often shares the ABS hardware

    Same system Supported by vehicle data

    U0122 is the equivalent lost-communication code for the vehicle dynamics module and appeared with U0129 on a 2024 Accord Hybrid.

  • U0121Lost communication with the anti-lock brake (ABS) module

    Same system Common general cause

    U0121 is the matching code for lost communication with the ABS control module.

All Module network (CAN bus) communication codes

U0129 questions

Can I keep driving with U0129?

Owners report red brake and ABS lights with it and some report odd braking behavior. If the red brake light is on or the pedal feels different, stop driving; otherwise have it diagnosed soon.

Sources and review

  1. NHTSA complaint ODI 11139911: 2017 Toyota Corolla — NHTSA (owner complaint)
  2. NHTSA complaint ODI 10357285: 2011 Toyota Camry — NHTSA (owner complaint)
  3. Toyota TSB-0325-08 (NHTSA 10027745): ABS, brake or 4WD light on with U0129 and P0500 — NHTSA (manufacturer communication)
  4. U0129 Missing Communication with Brake Control Module A (TaT Scandata) — TaT Scandata fault code library
  5. GM PIT5713 (NHTSA 10165919): engine wiring harness shorting at left front cylinder head — NHTSA (manufacturer communication)
  6. NHTSA complaint ODI 11589674: 2024 Honda Accord Hybrid — NHTSA (owner complaint)
  7. NHTSA complaint ODI 11298379: 2017 Honda CR-V — NHTSA (owner complaint)
  8. U0122 Lost Communication with Vehicle Dynamic Control Module (TaT Scandata) — TaT Scandata fault code library
  9. NHTSA complaint ODI 11737106: 2019 Chevrolet Silverado 1500 — NHTSA (owner complaint)
Last reviewed
Written by
Saurabh K.
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