U0129Network Communication

Lost Communication With Brake System Control Module

U0129 means a module has lost communication with the brake system control module over the CAN bus. Braking assist features are disabled. It usually points to a wiring, power, ground, or connector fault.

🚗 Not recommended. Losing the brake system module disables anti-lock and stability braking features.

HIGH

severity

🎯 Top Causes, Ranked by Likelihood

#1Wiring, connector, or CAN bus fault$50-$500

45%

Damaged or corroded wiring to the brake module.

#2Power or ground fault$50-$400

30%

Blown fuse or poor ground at the module.

#3Failed brake system control module$400-$1500

15%

The brake control module itself has failed.

🩺 Common Symptoms

Brake warning light
ABS and stability control disabled
Warning lights
Other U-codes stored
Reduced brake assist

💰 Repair Cost: DIY vs Shop

DIY Cost

$50-$400

Shop Cost

$150-$1200

📋 Free OBD2 Code Cheat Sheet

The 50 most common codes with likely cause and DIY fix cost. Sent once, no spam.

🔧 How to Diagnose U0129

1Check fuses, power, and grounds for the brake module

2Inspect CAN wiring and connectors at the module

3Scan all modules for lost-communication patterns

4Back-probe the CAN bus for correct signal

❓ Frequently Asked Questions

Can I drive with U0129?

Not safely. Anti-lock and stability braking are disabled. Diagnose it first.

What causes U0129?

Wiring, connector, or power/ground faults at the brake system module, most often.

Do my brakes still work with U0129?

Base braking usually works, but ABS and stability features are off. Drive carefully and repair soon.

🔗 Related Codes

U0121U0122U0128U0100