Basic checks
Veepeak OBDCheck BLE
A Bluetooth LE adapter for reading standard engine codes and supported live data.
View on AmazonU0129
Lost Communication with Brake System Control Module
High severity
The Brake System Control Module has stopped transmitting on the vehicle data bus, so other control units no longer receive its messages. ABS and electronic brake functions are lost; base braking remains but the assists are off. Typical causes are loss of power or ground at the module, an open or shorted CAN/LIN bus wire, a connector fault, or an internal module failure.
The Brake System Control Module has stopped transmitting on the vehicle data bus, so other control units no longer receive its messages. ABS and electronic brake functions are lost; base braking remains but the assists are off. Typical causes are loss of power or ground at the module, an open or shorted CAN/LIN bus wire, a connector fault, or an internal module failure.
Common causes
- high
Brake module unpowered
One of the most commonly reported causes for this code — check this first.
Typical part cost: $110-2200
- medium
CAN wiring to brake module broken
A plausible cause — test and verify before replacing parts.
Typical part cost: $110-2200
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First things to check
- 1Confirm the code with a scan tool and check for additional related codes.
- 2Inspect the relevant sensors, wiring, and connectors for damage or corrosion.
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Tools you may need
Already have a compatible scanner? Use it. If not, a Bluetooth OBD2 adapter can help you confirm engine codes and check supported live sensor data before replacing parts.
Regular diagnostics
vgate iCar Pro BLE 4.0
A Bluetooth LE adapter with an automatic sleep feature for routine code and sensor checks.
View on AmazonAnother option
OBDLink CX
A Bluetooth LE adapter to consider when comparing supported vehicles and diagnostic apps.
View on AmazonIllustrations shown, not product photos. Check vehicle, phone and app compatibility before buying. These adapters do not guarantee access to ABS, airbags or manufacturer-specific systems. Clearing a code does not repair the fault and can reset emissions readiness monitors.
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Related codes
See related trouble codes
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Frequently asked questions
What does U0129 mean?
U0129 means "Lost Communication with Brake System Control Module". It is a generic OBD-II code that points to a fault in the network / communication.
What are the most common causes of U0129?
brake module unpowered; can wiring to brake module broken; gateway module routing can messages incorrectly — these are the most commonly reported causes. Verify with a proper diagnosis before replacing parts, or use the Wrenchify app for a vehicle-specific diagnosis.
Can I keep driving with this code?
This code can put the vehicle into limp or reduced-power mode. Avoid extended driving and have the vehicle diagnosed promptly. Use the Wrenchify app for a full diagnosis specific to your vehicle.
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