What Does U0129 Mean?
Communication has been lost between the powertrain/body control modules and the main Brake System Control Module (typically ABS/ESC module). This network fault prevents brake system data from being shared with other vehicle control systems.
Safety Warning
Loss of ABS, traction control, and stability control functions significantly increases accident risk, especially in emergency braking or slippery conditions. Vehicle may also experience brake warning lights and reduced brake assist functionality. Drive with extreme caution and repair immediately.
Common Causes
35%
Faulty ABS/brake control module
30%
Corroded or damaged module connector or wiring
20%
CAN bus circuit fault or short to ground/power
10%
Power supply or ground circuit failure to brake module
5%
Module programming error or software corruption
Diagnostic Steps
1
Step 1: Verify brake control module has proper power (battery voltage) and ground using multimeter
2
Step 2: Inspect brake module connector for water intrusion, corrosion, or damaged pins
3
Step 3: Measure CAN bus voltages at module connector (should be approximately 2.5V on each line)
4
Step 4: Check for continuity in CAN-H and CAN-L circuits between brake module and data bus junction
5
Step 5: Attempt module communication through scan tool and check if other modules show network faults
Estimated Repair Cost
$200 - $1,200
Parts + labor, varies by vehicle and location
Communication has been lost between the powertrain/body control modules and the main Brake System Control Module (typically ABS/ESC module). This network fault prevents brake system data from being shared with other vehicle control systems.
The most common cause of U0129 (Lost Communication With Brake System Control Module) is: Faulty ABS/brake control module
Typical repair costs for U0129 range from $200 to $1,200, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Loss of ABS, traction control, and stability control functions significantly increases accident risk, especially in emergency braking or slippery conditions. Vehicle may also experience brake warning lights and reduced brake assist functionality. Drive with extreme caution and repair immediately.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to U0129 to identify the root cause.
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Quick Info
Category
Network
System
Anti-lock Brake System / Electronic Stability Control / CAN Network
Difficulty
Type
Generic (SAE)
Recommended Tools
OBD2 Scanner
A quality scan tool helps you read codes, view live data, and clear faults.
